This could be in any context, whether it’s aesthetics, how powerful they are in battles, etc.
My favorite is my Xu-fu. I like the way he looks and he’s pretty powerful, although I don’t use him as much. (Also, acquiring him was a lot of fun, too!)
Edit: Also, I made this thread because it’s Pokemon day, if anyone could catch that before this edit haha 
I adore Zao, but I’ve always really liked Niuzao. Though my all time favorite is still the Wind Rider Cub that came with the plush, he’s just too cute.
I don’t know, what I do is have a favorite pet or pets for each character. Melanin for example has a few pets on her toolbar. Arcane eye, emmigosa, arcane gorger, manafiend, lofty libram…
Xu-fu
Cinder Kitten
Ethereal Soul-Trader
Brightpaw
Lil’ XT. He destroys trains, has funny one liners, modeled off a cool boss in one of my favorite raids and he’s leveled just about every one of my 1000+ pets.
God I love my XT.
For just general awesomeness Ikky and Teroclaw Hatchling. Best looking pet that has to go to Brutus.
I’ve caused more 1st-turn rage quits with Little Ragnaros than any other pet.
But for looks, Zao
Phoenix Hatchling I won from Magister’s Terrace. I used to run him alongside the Fel Flame, so the Fel Flame would cast Scorched Earth to make the enemy team burning, then both pets can cast conflagrate.
Phoenix Hatchling is fast, deals a lot of damage, and its heal is incredible.
It also has nostalgic value and matches well with my mog.
Nexus Whelp. Use three of them and they can be quite formidable.
How come the ethereal soul trader is so expensive on the ah?
I’ve always wanted one
My Cinder Kitten. It’s really cute and playful and I like the fire elemental style.
My personal favorite is the Unborn Val’kyr. I like her looks and that she randomly raises dead critters that are nearby (nevermind that they don’t usually survive long since she like to do it when I’m in combat).
I enjoy the fight but I can’t stand his voice. I always had to mute my game sound when we fought him.
It is a TCG pet and you can purchase it on the BMAH.
Molton Corgi has clutched so many wins against boss pets for me that I can’t help but deem him as my favorite. Honorable mention to my Hyacinth Macaw because it is super rare, and I had to beg a GM to give it back to me because I looted a Murloc to see it pop up in the loot while on the quest to feed the baby raptor, and the raptor ate the corpse before I could actually bag it.
I have had auto loot on ever since. <3
Lifelike Mechanical Frostboar for me. I just like that it’s a boar and it’s mechanical and it’s frost. (I’m a dwarf engineer from a snowy area so yeah, we are jiving.) I named it Hogore. It might read like “Hogger,” but I pronounce it as Ho-gore just like Hodor from Game of Thrones. Just another layer of fun.
because it’s a TCG pet that isn’t available from any other source.
(might be on the BMAH occasionally? I’m not sure.)
I’ve said it before, I’ll say it again. Skanky is my pet and my dearest of friends.
Skanky is my spider egg infested, diseased and scarred baby bear from the Hillsbrad foothills. He so wretched and pathetic, only I could love him.
This feels like a Kaivax summoning thread.
I’ll allow it.
Also,
