When a person offers you a snack/food/something you don't like and you politely turn them down, and they flip their stuff.
People who smoke in a restroom. Seriously, save that stuff for your house. I used to rarely use restrooms because they're bad to begin with, but the smoke clogging the bathroom makes me never want to use it.
Me, when I wear my trench coat, for thinking I look stylish.
People that take your pencil/pen/something of yours claiming to "borrow" it and are never heard from again.
+Bonus points if it's an electronic of yours, which has happened to me from my supposedly good friends once.