The whole argument between 2e, 3e, 3.Xe and 4e. Let people do what they want. It shouldn't bother you that someone you'll probably never meet is doing something you don't like out of their own personal preference.
People that don't know what 'Mary Sue' means.
http://en.wikipedia.org/wiki/Mary_Sue. Learn you it.
The bad kind of furries(drama-spreading, cock-gobbling, 'oh, look at me, I'm different, you can't point it out without persecuting me for my ill-advised life choices' furfags; you know the kind). Keep your damn mouths shut and no one will care. Seriously.
Two more, just for shits and giggles:
Troll threads asking stupid/inane/pointless questions. Someone already pointed it out, but, 'OH, LOOK'.
General stupidity, wherever it happens(all of it, including, but not limited to, people that don't do their research, Chaotic stupid, people that use netspeak and people that put apostrophes in front of every S they type instead of using the actual plural term for the word). Fuck you all. You know who you are. Oh, wait, no, you probably don't.