I hate the:
-10 Year olds who try to call you a "fag" and a whole plethora of original names they got from reading comments on youtube.
-The ones that are just plain bad. And I don't mean the ones who got the game a week ago and they're learning the controls, I mean the ones who have no excuse for being that bad. I look back and think "man I was bad at this game once, but never THAT bad". I might sound like a bit of an elitist prick by saying this, but I know anyone who has delved into multiplayer and has experienced the guy who thinks shooting a wall is going to win the game agrees with me.
-The players who think they're so good, and talk themselves up to be some sort of Mesiah for whatever game they're playing, and saying you will never be as good as them...and they end up leaving because they have the worst score on the team, and then blame it on connection, yadda yadda yadda.
-I don't know if any other games experience this, but I am an avid Call of Duty player, and there are what's known as tryhards(just incase this isn't a universal term) who have names with lots of "ii"s in them, and alternating capital letters, which usually doesn't bother me (I am one of these men as you can see, lol), but when I see someone who goes entirely overboard with it it just kind of annoys me. ex. iiQWiiK Sc0p3zZz. Just names like that bother me for some reason. That's beyond wanting your name to look cool.
-Finally, another probable CoD exclusive is people in clans, with the clan name, and then followed by the clan name is some variation of one of these words, "scope", "sight", "fusion", or "magic". This may not have any relevance to anyone outside of the CoD community but those of you in that community have to know what I'm talking about.
That is about it for this rant.