I hate my damn group. I don't DM, but all of their behaviors are very irksome. The majority always play the same character, albeit with different stats and classes, and the ones who don't, don't really play at all. Just make attacks when needed and suck up XP.
Bill plays his Paladin as a Lawful Stupid tool.
Bob plays the same cleric of the same god in every single damn game.
Joe, powergamer supreme, seeks to screw around with the rest of the PCs as much as possible. (i.e. stealing the archmagus's prize possession we were trying to transport and hocking it on the black market)
Mort stands there. And does nothing. All. Of. The. Time.
Stuart's characters never have any personality. ("DM: The King is asking you to protect his daughter." Stu: "I don't know. High is yes, low is no."*rolls*)
Sam can't stand it when things don't go his way. Will often quit games because we don't wait for his late ass to show up.
Neil is always borrowing my stuff and not returning them. Makes me want to kill him.
Granted, I probably have mannerisms that piss them off, too. I can be really indecisive and sort of rules lawyerish, but mostly because they still don't know 3e rules.
I hate my DM, too. He has, at one time or another, been guilty of the following:
Deus ex Machina
PCs as Spectators
Railroading
Leading PCs around by the nose
Coddling his Damn Girlfriend's PC (20th lvl Fighter lover and her 20th lvl older brother)
Just Frickin' Cheating ("The Lightning Bolt that hit you didn't do enough damage." *rerolls*
God. I think I just left my group.