What Is Your Biggest Pet Peeve?

Do you have a pet peeve? Wikipedia.com say that a pet peeve  is a minor annoyance that an individual identifies as particularly annoying to them, to a greater degree than others may find it.
My personal pet peeve is when you are driving down the road and the person in front of you throws their cigarette butt out the window and they think that's OK. My second one is the person who is coming up to the intersection and you are trying to pull out and they do not signal that they are turning in! Come on a little courtesy would let me be able to pull out, but they just turn in like its no big deal. What is your biggest pet peeve?