Its probably pretty obvious by my signature (and the artwork I posted a couple of months back), but of the 25 babies in my burgeoning stable, the most special of them is without doubt Pokee - a Silithid Creeper I tamed in March of 2006.
While on my old warrior Calladra, I saw a dwarf hunter run past in IF with a scorpid and thought... wow what a neat looking pet! It wasn't as... shudder-inducing as an actual scorpion (they give me the creeps in RL, even Madexx does a little) and at the time I hadn't seen anyone else with one. So naturally I looked up where I could tame one! After some online perusing, I decided I liked the teal/greenish blue colored one best and so, I took my then-baby hunter Tyrith to Barrens where I quickly tracked them down.
Funnily enough, the scorpid almost maimed me on the first tame attempt. I didn't have much HP at all at the time, and so I had to run away. When I came back I remembered... oh that's right, I can tame from far away and use traps (dur, inorite)! My second attempt was successful and sure enough, I had myself a bright teal scorpid at my side, who didn't like me much at the time. I named her Pokee, after a plush animal someone dear to me has, and went about feeding her to bring happiness up. For days my goal in WOW was getting her loyalty up and I remember being all sorts of happy when I finally saw that Pokee reached best friend status.
Thing is, it was really hard to be taken seriously as a hunter at that point in WoW. Like, really, really hard. Hunters were notorious, even then, for being one of the most mistake-prone classes in the game. Getting groups on Tyrith seemed impossible at the time. To make matters worse my warrior was my guild's main, and so I was often bombarded with 'hey can u log Cally, we need a tank for <insert dungeon/raid/etc here>' requests which infuriated me. I felt like my hunter was basically invisible, even to my friends. The lack of other tanks in our guild began to make me feel smothered, because I had finally found a class I loved as much as my warrior. And Pokee was a big part of that.
I spent the vast majority of Tyrith's first 55 levels soloing - as dumb as I risk sounding, I very much felt alone on that toon. As those levels came and went, I guess it was a natural reaction to become attached to the only companion I really had at the time, Pokee. That little (or huge, rather) scorpid was the one thing I could count on when playing my hunter - Tyrith's best friend. I stopped caring about dungeons, or my inability to run them. Instead I developed a new love of questing and of challenging myself - I discovered then, before soloing was 'cool', that my hunter could do things on her own that tore my warrior to pieces without a healer. That I could tackle many group quests no differently than simple ones. Eventually my guild caught wind of my endeavors and we started doing dungeons with Pokee as the tank. We successfully cleared many places this way, including Scholomance, Dire Maul and Stratholme, and in L/UBRS my pet offtanked (who remembers when UBRS was a legitimate raid?). When pets got talent trees in 3.0.8, I was super-excited - seeing my scorpid get many of the same abilities and spells as my warrior just made my week!
Eventually my guild, like myself, came to legitimately care about my pet - I would log on and find TONS of meat and food in my mail from guildies and friends. Often I would log on and people would greet my pet first, lol, followed by a 'oh, hey Tyrith' which cracked me up. Pokee the scorpid had become a real part of my guild and of my 'lore' as a player of WoW. To this day she is lavished with affection (and meals) by players in my guild, has even tanked a handful of 85 dungeon encounters (Ozruk in Heroic SC being the one I am most proud of!) and also saved a few boss fights that went south for some reason (dead tank/healer generally).
Call me sappy, call me dumb, but I love the heck out of that little scorpid. Pokee is absolutely the single biggest reason I stuck with my hunter when I felt like giving up on her. And thanks to the surprising resiliency of tenacity pets in Cataclysm (far more so than ever) there are always lots of opportunities to show off her mad tanking skills. Whether its soloing stuff like Tank and Problim, or pet-tanking Crucible of Carnage for guildies and friends, Pokee will be a part of my WoW 'self' for as long as I continue to play the game.
Thanks for reading, those of you who do.

*edits for grammar/pacing*