Camp-Callers, it's a fucking legit tactic as far as I'm concerned and if you aren't smart enough to check around a corner before you run round blindly you deserve to die (in game that is, irl would just be hash).
And again, people who don't talk, maybe it's just me but when a multiplayer game is dead silent I just get really bored and think I may as well be playing bots, having random conversation or friendly banter is all part of the fun for me. Might annoy some people, but hey, you're free to mute me. Of course you can talk to much, but there is a balance, if its a team game tactics are needed.
And people who call BS all the damned time, I'll accept that games aren't perfect and will sometimes bug out, or lag might interfere, might even call it myself sometimes, sometimes I might even call it when I was on the winning end and admit I shouldn't be alive or whatever. But calling BS every other time you die? No, accept defeat graciously please.
Also, don't accuse me of having a small penis just because I killed you a few times, that's just plain childish.