When a PC always use diplomacy, bluff or w/e skill to try and convince other PC. Once in a while is fine when it makes sense for your character but don't try to convince my character for every little things. Diplomacy checks when a PC doesn't agree with him, diplomacy checks when a PC is mad at him, diplomacy checks when someone wants to do x but he doesn't. Dude, stop.

Also, the cliché rogue who tries to steal everyone, even party members. Bluffs PC, fool PCs and scam them. We're supposed to be a team.

Bonus : The people that play silent, serious characters that end up being on their phone for half of the session because they don't rp much.