Mostly chewing noises (my mother, although I love her dearly, chews like a cow); I don't like see-food, and the smacking is both gross and unhygienic. I don't understand how people can't chew with their mouths closed. For chewing gum, included.
Loud breathing (my brother is unfortunately a mouth-breather); I'm fine if it's across the room, but not if it's right next to me.
Loud snoring (I had to share a room with my brother for the longest time, and everyone in my house does it); however, after discovering that I snore too, I've been trying to become more lenient.
My neighbors' annoying, yappy dogs; they bark at the worst times of the day, and keep half the neighborhood up all night. Mostly, I'm mad at the neighbors for not caring for their pets like they should.
Loud, screaming, crying children, specifically young children. Really, I'm actually peeved at their parents for not attending to their children as they should. Especially if their child is purposely being rotten and rude and they won't discipline them for it.
Society's apparent lack of and utter disregard for basic hygiene; there's some nasty people out there. It doesn't take that long to wash your hands, cover your coughs, flush the toilet, or clean up after yourself.
People being rude and selfish for no reason; there is literally no reason to be a jerk in your day-to-day life, it is easier and healthier to be nice.
People who believe turn signals don't exist or think they own the road. The giant metal machines don't care if either of us go splat on the road; people need to practice looking out for each other and stop being careless.
I could go on, but I should go to bed
(which brings me to: early birds acting high and mighty towards night owls. We get it: you go to bed at 7pm and aren't plagued with insomnia and nightmares.)
(Note: If I sounded rude, I apologize; I've had no filter since March, and do not mean to cause hostility. )