If any new models or species are added that may be of interest to gnomes, I will update the post! :D
Pet Basics
For players who have never played a hunter before, here are some of the basics of pets:
Pets come in 48 different species, with plenty of model choices from each species. Eleven of those species are only avaiable to Beastmaster spec hunters. One species, the Direhorns, requires a book dropped from troll mobs on the Isand of Giants to tame. Some pets are easy to find, some are rare spawns that you have competition from other hunters (And other class players for whom Rare = KILL!) for, and there are even some pets that have unique challenges you have to overcome in order to tame!
You can only tame pets that are the same level as you, or lower. You cannot tame pets that are above your level. You can own a maximum of 55 pets. 50 can be stored at a Stable Master, and you can have 5 pets on your person at all times.
Starter pets DO NOT change when you race or faction change. So if you roll a tauren with a purple tallstrider and then later change to a draenai, you will still have your purple tallstrider and not a moth. Keep this in mind if you plan on leveling a hunter of another race and then changing it to a gnome! It may not come with any unique starter pets Blizz may decide to give us!
Pets have three talent trees you can choose from. While you can make any species pet any spec you want, some pets often have additional abilities that make a certain choice better for that pet.
Tenacity: Tanking. This ability gives your pet more stamina, more aggro abilities and more defense. They don't make good group tanks, but are best for solo content. Boars, Turtles, Bears, Crabs, Gorillas and Direhorns make great tanking pets.
Ferocity: PVE DPS. If you are doing dungeons and raiding, this gives your pet maximum damage. Cats, Dogs, Devilsaurs, Core Hounds, Raptors and Spirit Beasts are some of the top DPS pets.
Cunning: PvP. This spec gives your pet offensive and defensive abilities that are best in battlegrounds and arenas. Silithids, Chimeras, Birds of Prey and Spiders are some of the top PvP pets.
Right now most species of pets come with stats they can provide for groups. These are being removed entirely in Legion so I won't waste space discussing them.
If you want to learn even more about pets, what raid stats pets will give out until Legion's release, families and models not listed before and more details, check out the bible for Hunters and pet lovers everywhere: Petopia!
Gnomish Pets
Here are a list of pets that I think will fit someone who wants a pure Gnomish asthetic for their future hunter. Remember even as a gnome you don't need to tame these. Tame what you want and models you like! Tame all green pets for your green-haired gnome. Tame only herbivores! Or don't go with a theme and just tame whatever models suit your fancy!
Gem Owls:


These gem owls looks like they have been been carved from stone, gem and metal. It comes in blue, green and transparent green models.
Species: Bird of Prey
Blue Sapphire Model: Quall - Level 25 Rare in Stonetalon Mountains.
Green Jade Model: Emerald Skytalon - Level 73-74 in Dragonblight. Alystros the Verdant Keeper - 74 Elite in Dragonblight.
Transparent Jade Model: Emerald Spirit - Level 25-26 in Stonetalon Mountains.
Armored Boars



Available in black, grey, brown and ghostly brown. I picked these boars because you can always say your gnome has cleverly created it's personal defense armor system themselves!
Species: Boar
Black Armored Model: Finn's Gambit - 16 Rare in Silverpine Forest. Battle Boar - 33-34 in Razorgen Kraul. Scruff - 36 Rare in Dustwallow Marsh.
Brown Armored Model: Amored Battleboar - Level 3-4 in Mulgore. Swee - 27 Rare in Arathi Highlands. Battle Boar - 33-34 in Razorgen Kraul.
Grey Armored Model: Battle Boar - 33-34 in Razorgen Kraul. Hogzilla - 47 Rare in Searing Gorge.
Transparent Brown Armored Model: Boar Spirit - Level 27 in Razorfen Kraul.
Gem Cats:


These metallic cats can offer some of the best oppertunities as a mechanical pet! A good example was a goblin in my Horde guild pretended it was an Engineer-made robotic feline. The black cat can only be found in the Molten Front, so make sure you unlock that content!
Species: Cat
Black Gem Model: Skarr - Level 85 Rare in The Molten Front.
Green Gem Model: Jade Guardian - Level 85 in The Jade Forest.
Armored Chimera:




These chimera are armored from head to toe and give off a fantastic robotic look! Chimera's are Exotic beasts though so you must be Beastmaster to tame and use one! Also a Chimera is a MUST if you solo the old raid Temple of Ahn'Qiraj. Their unique ability Froststorm Breath & Frost Breath is the only way to freeze and kill Viscidus for his vanity pet on your own!
Species: Chimera
Green/Brown Model: Vilewing Chimaera - Level 68 in Shadowmoon Valley (Outland).
Purple/Black Model: Norissis - Level 51 Rare in The Jade Forest. Nuramoc - Level 60-70 Rare in Netherstorm.
White/Blue Model: The Razza - Level 40 Rare in Feralas. Ronak - 53 Rare in Winterspring.
Yellow/Brown Model: Bladewing Bloodletter - Level 64-66 in Blade's Edge Mountains.
Gem Crabs:


These crabs are ready to grab your foes in their mechanical claws! I don't think they go very well with tartar sauce though... The black crab is a rare from the Molten Front do be sure to unlock it!
Species: Crab
Black/Red Gem Model: Karkin - Level 85 Rare in The Molten Front.
White/Blue Gem Model: Moonshell Crawler - Level 90 in Shadowmoon Valley (Draenor). Glass Crab - Level 100 in Nagrand (Draenor).
Lightning Crabs:


If you're prefer newer model crabs, these are your go-to guys. Their stone like appearance is enhanced with glowing, electric-like designs on their bodies. Enhanced by a gnomish device gone haywire perhaps?
Species: Crab
Blue Model: Luminescent Crawler - Level 90 in Isle of Thunder.
Purple Model: Guardian of the Deep - Level 25 Elite in Blackfathom Deeps. Luminescent Crawler - Level 90 in Isle of Thunder
Outland Hydras:





These three headed goliaths from the depths have a very hard time agreeing with eachother, as such the main issue I have with this pet is they constantly make noise. But if that doesn't bother you, their mechanical looks may go well with your gnome!
Species: Hydra
Blue Model: Mire Hydra - Level 60-61 in Zangamarsh. Fenclaw Thrasher - 62-63 in Zangamarsh.
Green Model: Ghaz'an - Level 65-61 in The Underbog. Leviathan - 72 Elite in Black Temple.
Grey Model: Mragesh - Level 64 in Zangamarsh.
Orange Model: Parched Hydra - Level 61-62 in Zangamarsh.
Purple Model: Markaru - Level 68 in Netherstorm.
Chimaeron:

Oh my, it looks like your gnomish experiments went a little haywire on this subject... this Hydra is a raid boss that is hard to tame even at level 100! Make sure to take at least one other person with you, preferablly a healer!
Species: Hydra
Chimaeron: Boss in Blackwing Descent, I suggest level 90+ to tame safely.
Fez Monkey:

Because Fez's are cool, no matter what race you are. All he needs now is a bowtie and a sonic screwdriver.
Species: Monkey
Fez Monkey: Gib the Banana-Hoarder - Level 52 Rare in Swamp of Sorrows.
Quilen:







There are three model types of Quilen in the game, a natural looking one that isn't of much interest to gnomes, and then there's a Stone and Armored Stone version. The regular stone Quilen are all one solid color, and the armored versions have colored collars and bracelets on them! Quilen are Exotic so you must be a Beastmaster, plus they have a special skill that can rez players!
Species: Quilen
Solid Blue Model: Quilen Watcher - Level 90 in Rare in Crypt of Forgotten Kings.
Solid Purple Model: Terracotta Defender - Level 87 in Kun-Lai Summit. Quilen Statue - Level 90 in Rare in Crypt of Forgotten Kings.
Solid Stone Model: Waaay too many to list. Most are level 90 in Vale of Eternal Blossoms.
Armored Models: Portent - Level 90 Rare in Vale of Eternal Blossoms. Will be a different color every time he spawns. Stone Guardian Bosses in Mogu'shan Vaults, level 90+ to tame. Only three out of four colors will be present in each week.
Armored Rylak:

This is the same model as the Iron Skyreaver mount but in a rich red color. Aside from it's armor it comes complete with a jet pack attached! Rylak's are exotic so make sure you are Beastmaster to tame and use it!
Species: Rylak
Armored Rylak: Tura'aka - Level 99 Vignette Rare in Nagrand (Draenor).
Molten Scorpion:

This scorpion touts a unique metallic color with the added bonus of looking like part of it's body is molten!
Species: Scorpid
Molten Scorpion: Blackshell the Impenetrable - 45 Rare in Badlands. Duneclaw Broodlord 47-48 in Tanaris. Snips - 49 Rare in Searing Gorge.
Gem Scorpion:

This black and orange scorpion looks like it was forged from the Kyparite and Amber of the Klaxxi. The black parts of it's body look like it could be descriped as heavy metal plating.
Species: Scorpid
Gem Scorpion: Ik'thik Amberstinger & Ik'thik Terrorclaw - 90 Elite in Dread Wastes. Kor'thik Scorpid & Zan'thik Amberhusk - Level 90 in Dread Wastes. Kri'chon - 91 Elite in Vale of Eternal Blossoms.
Fire Turtle:

It's rock-like shell is covered in fire and molten looks, with the skin underneath cracked and glowing. I also believe it may smoke! A perfect pet for your engineer to smelt their ore over.
Species: Turtle
Fire Turtle: Terrorpene - Level 81 Rare in Mount Hyjal.
Armored Wolf:

This steel and fire covered wolf comes ready for battle. Aside from it's mini battlestar and front-facing metallic fangs, it also comes complete with it's own toaster built into the front of the saddle!
Species: Wolf
Armored Wolf: Iron Warwolf - Level 100 in Tanaan Jungle (Iron Front).
Lightning Wolves:


These wolves share a model but are two seperate families! Perhaps they got their electrostatic charge from a gnomish device gone haywire! The darker colored model is a Beastmaster-only tame under the Spirit Beast family. The paler is under the wolf family and available to all hunters.
Species: Wolf (Thundermaw) & Spirit Beast (Skoll)
Spirit Beast: Skoll - Level 80 Rare in The Storm Peaks.
Wolf: Thundermaw - Level 90 in Vale of Eternal Blossoms. Cracklefang - Level 91 in Vale of Eternal Blossoms.
Silkworms:





There's no actual gnomish reason for this choice. I just think these little baby worms with gnomes will look adorable with a gnome hunter.
Species: Worm
Blue Model: Mottled Caterpillar - 85 in The Jade Forest. Spotted Caterpillar - 88 in Townlong Steppes. Siftworm & Giant Siftworm - 90 in The Jade Forest.
Green Model: Bookworm - 85 Spawned in The Jade Forest. Spotted Caterpillar - 88 in Townlong Steppes. Frenzied Caterpillar - 90 Spawned in The Jade Forest.
Purple Model: Bombyx - 90 Rare Elite in Krasarang Wilds.
Red Model: Mutated Silkworm - 86 in Valley of the Four Winds. Spotted Caterpillar - 88 in Townlong Steppes. Frenzied Caterpillar - 90 Spawned in The Jade Forest.
Yellow Model: Chibee - 85 Elite in The Jade Forest (Is larger then any other silkworm tame). Spotted Caterpillar - 88 in Townlong Steppes. Frenzied Caterpillar - 90 Spawned in The Jade Forest.
New Legion Models
New Stone Scorpion:

Could this be a new mech model? Or will it just be a stone scorpion under the scorpion family? It'd look good with a gnome regardless!
Mechanical Pets

Gnome Hunters and Mechanical Pets have officially been 100% confirmed! Click Here to Read the Official Announcement!
Here is a rundown of what we know so far:
- Gnomes and Goblin Hunters will be able to tame mechanical pets right from the start.
- Other races will require the Mecha Mind Synchronization Fluid pictured above to tame mechanicals.
- The item will be created by Engineers. Materials, cost and so on are not yet known.
- The article states that they are "artificial animals", so they will not include things like shredders, mechagnomes and bomblings, only those mechanical mobs that are designed after animals.
- The article states Mechnical pets are hard to find. Which I translate to rare spawns, and also not having many models to choose from, at least at release.
- Most, if not all, Mechanical Pets will be Challenge Tames.
Confirmed Pets
Giant Mechanical Rabbit:

This rabbit will be the starter pet for newly created gnomes. As of this time in the Alpha (5/8/16), this model is not tamable anywhere else in the world. Until we can see any information that it becomes tamable, it is worth it to note that any race that is race changed to a gnome in Legion will NOT have this pet. If a tamable spawn is found during the Alpha/Beta, I will update this!
Species: Mechanical (Rabbit)
Proto-Strider:

There are two Mechanostrider pets to tame, and this is the easier of the two. It is a simple basic tame located in the Ironwing Cavern in Loch Modan.
Species: Mechanical (Mechanostrider/Plainstrider)
Optimo:

Optimo is a rare spawn inside of the Ironwing Cavern in Loch Modan. He can be found running through the entire cave so he doesn't have any specific location he can be found. It's also of note that his color is unique, as the mounts do not come in his coloration.
Species: Mechanical (Mechanostrider/Plainstrider)
Tekton:

Located in Elwynn Forest, you may remember this guy as the sheep located in the mountains you could only get to by flying, and killing him caused an NPC to yell at you. Well, he's still there but now he is tamable and got a model upgrade. He will have to be crowd-controlled just before taming starts with Freeze Trap or Binding Shot. If he reaches you he will explode and knock you back.
Species: Mechanical (Sheep)
Treble:

This black mechanical wolf is similiar to rare pets in Pandaria. He is hidden from sight and you have to track him by puddles of oil. When you find them, track them until you see them appearing in front of you. Throw out your flare, and when he appears in it, use your Freeze trap or Binding shot. He is located in Highmountain.
Species: Mechanical (Sheep)
Rush:

Rush follows the same taming mechanic as Treble, you have to track him via oil puddles. He is located in Northeast Azsuna.
Species: Mechanical (Wolf)
Friender:

This blue mecha-wolf is located deep inside the Gnomeregan Dungeon, specifically the Engineering Lab. His level scales to yours so don't expect to go into it and find a low level pet if you are far above the dungeon's level. He will be sleeping and you will have to wake him up in order to tame him. There are three buttons you have to press in a certain order, and the order will change every time you reset the dungeon. There may be a bug and you may have to reset it a few times. Once awake he runs around the room in circles. He cannot be crowed controlled and hits very hard, so best bet is to hit Aspect of the Turtle just before taming.
Species: Mechanical (Wolf)
Haywire Battle-Chicken:

Also located in Ironwing Cavern in Loch Modan is the Battle Chicken. They are a basic tame however as of right now they are still the low-resolution model.
Species: Mechanical (Chicken)
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Speculative Pets*Speculation!*
These pets are all currently models from vanity pets (except for A-Me), and none are guaranteed to be hunter pets. However, these are the only mechanical beast models in the game aside from A-Me 01, so I would expect Blizzard to at least use one or two models. Please take these with a grain of salt and speculation!
Mechanical Gorilla:

This is the only "true" mechanical hunter pet that currently exists in game. It's a mechanical gorilla model, and as of now it's listed as mechanical and thusly unable to be tamed by ANY hunter. Hopefully this skin will become available to the mech family. This gorilla is A-Me 01 in Un'Goro Crator, the focus of a quest.







Taming Challenges:
Since most of the Mechanicals will be Challenge Tames, I will highlight some of the current Challenge tames in the game so those who have never played a hunter will get an idea of what they are and how they work.
Ban'thalos: Spirit Beast - Ghostly Green color with wing trails. Ban'thalos spawns Mount Hyjal in the outside area near the entrance to the Molten Front. His tame is simple, yet tricky. He flies high enough in the air that the hunter needs to creatively think of a way to aggro him and not sustain lethal fall damage, or land with enough HP that when they are hit by the owl they are not dead within a few hits.
Anhka & Magria: These spectral saber tiger Spirit Beasts in Mount Hyjal are hard tames. "The better prepared you are for Anhka, the more damage he does to you" which means you will actually need to remove ALL your armor to tame him. Magria is the same, except he has a faster attack speed then Anhka.
Porcupines: These ghostly Pandaria porcupine Spirit Beasts all require to have their health reduced to 30%, kiting is necessary as he hits HARD. They also run hard so Aspect of the Cheetah is a requirement. Scatter Shot and Entangling Roots have no effect on them.
Karkin: Mentioned in the "Gem Crabs" above, this black stone crab in Molten Front requires the hunter to silence their Fieroclast Barrage ability in order to tame.
Molten/Stone Spiders: These unique spiders are all rare spawns in Molten Front, and have hard taming challenges unique to each color. Skitterflame (Red): Skitterflame must be kited to reduce his "heat" energy bar before taming. Solix (Yellow): Hiding in lava. Solix has a buff that increases his attack speed by 1,000%, and he must be kited until the buff drops and quickly tamed before he dies. Kirix: (Green) You have to dodge rocks and thermal vents while kiting, and you'll need to use Deterrence to block his toxin and then cast Tame Beast while under haste effects to tame as quickly as possible. Anthriss (Orange-Yellow): Anthriss requires you to submerge in the lava to avoid his webs which turns him into an easy tame. Deth'tilac (Purple): Deth'tilac is a big bad spider that is best tamed with a group. His Death Strike ability instantly kills the target, but lowers Deth'tilac's health.
Pandaria Rares: There are an assorted number of pet rares in Pandaria, one per zone. They are completely invisible to non-hunters. They are invisible to hunters too, but hunters are able to see and track the paw prints these beasts leave behind. If the hunter casts a flare in the path of these pawprints, the beast will appear but has to be tamed before they walk out of the area of the flare and disappear again.
Gara: This purple Draenor model wolf Spirit Beast is the newest and by far most advanced challenge tame in the game, as it's a series of hidden quests! The steps to taming him are too long to mention here, so click here to check them out yourself.
Everything below this logo will be a potential spoiler for Battle for Azeroth!

The Beta files just went up on January 26th and I will post up gnomish models of interest when I see them come up! Also forgive the white fuzziness on the images, I got a new art program and am still messing it's settings around.

A new robotic kitty to go with your robotic doggy!

A brand new robotic chicken model was added too!

Frogs are finally getting a model upgrade, and a lot of different colored mechanical ones are included!

Many old models are getting new versions, crabs included. Here's a nice stone/mechanical crab!

The groundhog/gopher is not immune to the new models as well! Hello mecho gopher!

Non-hunters don't feel left out! A mechanical version of the Creepy Crawling Hand is here!

A new mechanical flying machine, even if it is a goblin made one.

The goblins also got jealous of Mimiron's Head.

A simpler model version of the Argus light glowy one whose name I can't remember.

Not hunter related, but good news - I think! Gnomes now have their own skeleton...! ...Yay? Dwarves, Goblins and Tauren have new unique skeletons too so far!

Also not hunter related. Bee mounts are coming. Can you imagine an army of gnomes on bee mounts? So cute!
Have any other pets you think may be of interest to gnomes? Wanna leave any additional pet tips? Have any hunter questions you wanna ask? Don't hesitate to reply with questions or additions! :D