What is your biggest pet peeve?

Personally there are two things that really gets on my nerves.  One of them is people who do not go put their shopping carts away when there are done putting their purchases in their vehicle. Everyone things this one is odd for me because I do not drive but it does get on my nerves.  

The other pet peeve is people who wear hats in restaurants.   One time we were having breakfast at Denny's and there were at least 10 people wearing hats in the place. I swear it is a good thing I am shy because I would have went to tell them all to take their hats off. Sure it was winter but they were in a warm restaurant so there was no reason to be wearing hats.

Anyways I think those are the only pet peeves I have, or at least the big ones.   What are your pet peeves?