Loud chewers or worse, open mouth chewers. Or talking with a mouthful.
People who inhale food, not bothering to chew it. No one will steal it!
People who keep asking all kinds of questions during a movie. I you just shut up and listen, you'll be able to follow.
Someone asking the same question over and over again. I didn't know the first time, asking again won't make me have an epiphany. Or worse, I answer it once, didn't you listen?
People who talk and talk and talk without making a point, clarify an idea or just listen to their own voice, amazed at their own genius. I work with someone like that, I want to slam my head against my desk everytime he comes near.