When driving, what do other drivers do that really annoys you?

Piggybacking on my other question about what annoys you in your every day life, I came up with this.

What annoys you that other drivers do when driving?

Someone on the other thread mentioned people going slow in the left lane, and I’d say that’s number one for me, too. Especially when there’s nowhere else to go because people in the middle and/or right lane are going at the speed they’d like to. People in the left lane going slowly are either clueless or stubborn. Very annoying. Again, I don’t get mad at much but this really irks me.