How about those oh so courteous folks who fly past you, pull into your lane, and promptly put on their turn signal. Notice that usually in such a case there will be no one behind you for miles.
My peeve — on single-lane roads with passing lanes, the people who drive really slow on curves and non-passing sections, and then accelerate to 10mph over the limit where the road is long and straight enough to pass.
I know that it is likely they are simply driving as fast as they feel safe, and aren’t purposely trying to prevent people from passing. (You know that type, they wait until you are halfway past them and then they speed up to make it hard for you to get by). But it’s still anooying.
Whenever I see someone passing, I slow down to make it easier for them.
Also annoying — people who pass you in a passing lane, and then drive slower than you were driving.