People who are too obnoxious about the small things that bother them.
I had a friend in high school who was really over the top about all her little quirks. Like, if you folded a piece of paper wrong or didn't lay something straight on a desk she'd freak out and try to fix it, and if you resisted she'd be like, "ohhhhh it's going to bother me so much because it isn't right!!!" like you'd committed a cardinal sin or something.
I also hate when people try and correct you mid-sentence when you don't pronounce a word the same way they pronounce it. It's like, fuck you, unless it's your name I mispronounced, I don't need to be corrected. Just silently correct me in your head and let me talk!
As for a real pet peeve, when the windshield wipers are on when it's not raining (or not raining hard enough) and they make that horrible squeaky noise against the glass.