People who walk really slowly in front of me. Especially if they walk side-by-side in large numbers. Especially if they're smoking and the smoke is blowing back in my face. Urgh.

People who chew with their mouth open, making smacking noises. Especially if they are chewing gum. Especially if they're also the kind of people who don't bin their gum.

People who use headsets/headphones that don't contain sound well. Especially if they play music loudly. Especially if they're on the bus. Especially if it's a long journey. Especially if they have terrible, terrible taste in music.