Not stuff people do to you. Stuff you do to others. As in, what mistake, when you make it, bugs you the most? Shit happens and we all make mistakes, it’s OK. But some make you wish there you could get out and apologize profusely to the affected motorist.
For me, it’s when I get in someone’s way. You’re moving faster than me, I’m busy with an overtake of my own and therefore in the lane you want? I’ll usually speed up. Someone’s waiting behind me at a turn? Stuff like that really bugs me if it goes on for too long (I’m going to say 15-20 seconds. Time it. You’d be surprised how fast traffic actually does move. 15-20 is a fairly long span, though not extreme by any means.) and it put’s me in a practically helpless situation. I can’t go ahead and I can’t let the person go by me. I’ll often rug it for a smaller gap than I would normally take in that situation, just so the guy behind can have their turn.
On the other hand, this often leads to “do unto others as you would have them do unto you” situations, but in reverse. I try my best to stay out of your way. I expect you to stay out of mine.