I'm a pretty docile personality, but I do get somewhat upset when people do really stupid stuff, like the car last week that decided to cut around me right after I signaled a left turn I was just a second from starting. I was going uphill, so I couldn't signal THAT far in advance without losing all my momentum, but he had no excuse for that, he had plenty of time to decide to wait a couple more seconds for me to turn and get out of his way. Almost yelled "thanks a lot" at him.
The other thing that gets to me is when a deer is hanging out in the grass strip between the road and the sidewalk and I never if or when it might dart out. I've had them jump right in front of me, so I always go really slow past deer if moving left isn't an option due to cars. The deer in our town are a serious problem.