Huge per peeve for me. Hands down, the guy going too fast. He almost went over the edge in a place where he'd have been certain to roll his vehicle when he met me on that blind curve. I ended up in the inside ditch. At least he stopped to make sure I could get back out, apologized and admitted he was a "moron". I accepted the apology but didn't argue with his self-assessment.
With that said, a little consideration and patience goes a LONG way. If someone is behind me, I pull over and let them by and if someone slower is in front of me, a little couple deep breaths and a little patience until they can pull over safely for their vehicle.
Maybe I'm doing it wrong, but "race", "hurry", "deadline", and "schedule" aren't words I associate with overlanding.