I don't find perks or weapons or anything to be the most annoying part of MW2, but rather people who just go for revenge kills. I'll kill someone in a particular spot and then they'll immediately go for me again because they're pissed off. However, the ways in which they kill me relates back to annoying perks and such. I can't tell you how many times I've gotten knifed or noob tubed on a kill streak just because someone wants to get revenge. But, camping kind of goes like this: If the dog bites you once, it's the dogs fault, but if the dog bites you a second time, it's your fault for going near it.