1) Talking with a full mouth.
2) People singing obnoxiously loud to themselves while running on the treadmill. Unfortunately, I was next to one such guy for 50 minutes and could hear him over my headphones. He thought he was Steve Perry when in reality he was a croaking frog.
3) People talking on their cellphones when they're in line to order food. Have your order ready to go before you get there! The worst is when they're having random chitchat while the employee behind the counter waits for them to finish their conversation.
4) People who pass you on the interstate and once they're by you, they immediately slow down such that I end up passing them a few miles later. If you're going to blow by me, keep your speed constant!