I had a guy give me the finger once because he thought I had speeded up while he was passing. He gradually slowed down and motioned for me to pull over to the side of the road. I did, and then he jumped out of his car and came running over to mine shouting and cursing.
I got out and told him he was wrong, that I hadn't speeded up at all. Before I could say anything else, he threw a punch at me. I'm definitely not a fighter, but I do try to defend myself. (I think that most of the time, the worst thing a person can do is run away from a fight.)
His punch just missed my head as I jerked back, then I leaned foward and smacked him in his left eye.
He sat down by my car and started crying and apologized for starting the trouble. He said his boss had chewed him out that day and so he was just in a very bad mood. We talked about it for awhile and he apologized several more times and swore it would be the last time he stopped anyone because of his temper. We ended up laughing about it and left in a good mood.