When I play online, I play mostly L4D2 and TF2. In TF2, you can't really only play with your friends, there will always be some random, if you play like I do, and I have no problem with people that play TF2, all seem to be nice people there... mostly. I can say I have never ran into an annoying person there.
But Left 4 Dead 2 is another story... COMPLETELY another story. Just press Quick Game on any of the game modes, and you'll propably run into some of these:
People who take it too seriously. I have no problem with wanting to win, but when people start swearing on the chat becouse someone failed; is just stupid. And if you faile twice or more, then you're sure to get kicked.
12-year-olds playing it... nothing really against them, unless they talk on the microphone with their helium voice all the time... and leave the mic on even thou they are not talking, that's just annoying. To just hear the buzzing the whole time you are playing...
Foreign, who just can't talk engilsh with the team. ONe itme this russian guy just talked russian all the time, trying to give instructions to the rest of the team, but I was there trying to tell him to please talk english so that I understand too. Did he? No. He kept the language russian. Then when I die, he talked his first sentence in english, telling me, that why I didn't do how he told me to do, just assuming I understood russian, even thou I told many times, that I don't and would we please talk in english, becouse we all peopably understood it.
Ragers... no need to introduce them. Oh and rushers too.
So yeah. That's why I always try to find as many friends as I can, to get playing with me. But you can't always have it that way can you?