One thing that really annoys me is when people turn on their signals as they turn, as if it matters at that point.

They’re meant for indicating that you’re about to turn or change lanes, not for notifying other drivers that you’re doing something that they can already see you doing. I’ve ridden as a passenger with numerous drivers that have gotten angry at other drivers for “not letting them in” and yet they never turned on their indicators to show that they even wanted in in the first place.