So, here we go:
-Character death. I won't read it. In any context.
-Anal with no prep and then the guy being fucked gushing about how gooooood it feels. 'Cause it DOES NOT and all I can think of is PAIN and OUCH and the moment is ruined.
-The word dribble. As in..."come dribbled off his chin." Eewww.
-Grown men giggling. This makes me want to hit something.
-Adult/child sex in any context but especially Daddy!cest in SPN.
-People who post fic full of errors and then say they "couldn't find a beta." Seriously?
OK, that's all I can think of off the top of my head. Your turn!