Things I hate:
The Crapshooter: Everytime this player has to roll the dice, he thinks he's at the craps tables in Vegas and rolls the dice so hard they roll off the table. I ran a short capmaign in which EVERY freakin' player did this.
The Percentile Cheater: When you have to roll 2d10 for a d100 roll, this player always declares which die is which digit AFTER making the roll. This is why I switched to those nice d10s numbered by 10s for d100 rolls. The Percentile Cheaters were not pleased.
No Immersion: Must name character after a wrestler or some other goofy-ass real world thing that sticks out of my campaign like a sore thumb.
Mr. Splatbook of the Month: Doesn't have any real concept for the character except for trying to add whatever feat/PrC etc from the latest splatbook he thinks is cool. Related is is the guy who gets bored with his character after two sessions and wants to roll up a new one.
Lovebirds: The dating players who make out at the game table.
Ones that have been mentioned:
The guy that is always in perfect range for melee attacks, but is nowhere in range at all when he gets attacked. Or a trap goes off. Gets cranky when I insist on miniatures.
Overdeveloped: has a character background that is so overdeveloped, he doesn't really fit into the campaign. And there's no logical reason for him to follow a plot hook. I also don't like the "My character would never do that", or the RP types that go out of their way to build a charater that does NOT work in the campaign or with the other characters.
Monty Python quoters: for the love of God, stop introducing this movie to nerds! I don't think it's that funny at all, and I get tired of people quoting it. Other movies are ok though...
People who get picky about OOC/IC talking. Lighten up people, it's just a game and a social activity. It's annoying when the blathering derails the game sure, but people who take the game and their character too seriously are annoying.
Badass loner: again it's a group activity. Stop thinking this concept is at all cool to the rest of us because you can't get laid.
The guy who can't be bothered to learn about the campaign world or the current campaign, or any relevant house rules.
As for me, I'm "guilty" of the recycled and generic characters. But I don't see this as a problem. First of all, there are certain concepts I like to play, and I play them. That's what's fun for me. Do NOT make me play an elf bard because you want to see me play something different, because I'll just get the character killed and go back to my human/dwarf/gnome fighter/paladin/wizard. As for generic, I want to keep the character loose enough so he can be flexible with development as the campaign progresses, unlike the character concepts that are so tighly constructed that the force the campaign to work with them, rather than try to be part of the campaign.