I would have to say the most annoying aspect of gaming, especially on FPS, is the cheating. People complain about campers, noob tubers, rambo teammates, and other generally annoying people you encounter in the game but the difference between that and cheating is you can't prevent cheaters in the game but you can always do something to prevent the other little annoying things. For instance, if you are well prepared going into a match you'll have a class with flak jacket for noob tubers, blackbird for campers (sorry the last game I played was black ops), and I always go into games with a full team to avoid random idiot teammates.