^This.

Though I'm a pretty mellow guy, so it's not enough to keep me from playing. 

My games usually never lag, so nothing much at all.

Slow broadband, lag, glitches, people getting their ass pwned on a continuous basis, taking up too much of your free time- highly addictive experience, annoying people online,etc.

Heh, you list noobs on the top.

I would like to add fees, immature people, racists, and that pretty much somes it up

Voice chat is awesome.

If you play competitive games, then maybe it might not be good, but it's necessary in almost any team game like Team Slayer on Halo 3 or Team deathmatch on CoD4.... You need to know what your teammates are up to.

FC and Lag

 lol. that guy in your sig, i dont even know how he can go outside witout getting beat up by marioboys and halo nerds after what he said about 360 and wii on his video on youtube.

and ye i really do hate fees, *cough...xbox live cough*\. when i had my xbox 360 i had to fork out 68 bucks for live canadian dollars and i didnt even use it for half a year. 

Sounds like we have a lot of XBL players here :D
Come on over to PC gaming, it is markedly better (as far as the players' behavior goes)

I don't like having to play against people who have played the game for hours a day since the game launched....they've specialized so much in what they do that there's just no point trying to compete against some of them.

I also hate teammates that get mad so easily if you don't help them in time, or people who get mad because you keep beating them.

 Ugh, I couldn't agree more. I normally don't mind trash talking, but somehow when it's coming out of some little kid's mouth it becomes that much more obnoxious.