Everyone has the one class or spec that they dislike irrationally. You call for them to be nerfed on the forums, you stalk them through battlegrounds, and you may even swear under your breath when one of them ends up in your instance group. This is your archnemesis class.
There's an old joke that the traditional enemy of the rogue is every other rogue on the server, and I have to admit that used to be true for me. I hated other rogues more than any other class. Sure, there were really nice and skilled rogues, but they seemed to be in the minority compared to the giant amount of idiots that rolled a rogue to be cheap shot artists (pun intended.) All the ninjas, drama queens, and overall irritating people I met in my first few months of playing WoW were other rogues, and a deep sense of self-loathing festered inside of me. I was halfway tempted to reroll a warlock -- and this was back in the days where NO ONE was a warlock -- when the idiot rogues disappeared! Where did they go?
A couple months later, when untalented, unintelligent, aggro-insensitive DPS warriors began infesting my guilds, I had my answer. To this day, I'm always a little suspicious of DPS warriors, particularly those who utterly refuse to consider tanking an instance and have a wishlist consisting of 90 percent of the one and two-handed weapons in the game. However, the recent warrior nerfs have sent the annoying DPS warriors back into hiding, soon to emerge again as whatever other class allows them to take a lot of loot and smash things.
What class/spec annoys you most in WoW? Does the annoyance extend only to people you fight in PVP, or do you hate those of the same faction as you?