competition: What really grinds your gears?

I have a lot, but I'll try and narrow it down :]
*Carlos Mencia - he's not funny at all and all he does is yell
*People chewing gum really loud and with their mouth open!

Here's a big one: I work at a grocery store, and we close at midnight. Sometimes I will work 'til closing, so I really hate it when people will come in a minute or so before we close, and we let them know they only have that amount of time to get their thing. But what do they do? They take their sweet ass time making me late to clock out.
People are so rude.