People who shove their way into public transit trains when obviously there's a huge mob of people waiting to get out first.

Here's a big one: the sound of gnashing teeth against cutlery, especially tilting when it's a spoon. Why are you biting your soup? I used to do this when I was a kid and thankfully was taught by my parents not to do it. I did it because eww lips against metal that other lips have touched eww germs. Therefore I have this theory that virgins have a higher likelyhood of exhibiting this behavior.