I do NOT recommend this to anyone.
I have since learned the valuable lesson that *most* times a motorist pi$$es you off, screams or honks at you, or generally tries something ***anine or shady, it IS BEST to ride off and forget it. Unless, of course, some harm came to you or your bicycle. In that case, just call the police.

So I was riding along around rush hour (chicago) on a side(ish) street with no bike lane. Since the speed limit here is 25MPH and there are stop signs at every side street intersection, I ride in the middle of the lane as if I were a car. Usually no problems with motorists as I am usually faster or as fast as them.
This guy in a BMW SUV starts revving his engine WAY up, over and over behind me and lurching his vehicle up toward my rear tire repeatedly. I turned and looked at him and patted my hand toward the ground (like 'OK, cool down buddy). I could tell by the look on his face that he was JUST PI$$ED about something. Maybe it was the 4.50$ a gallon gas, I don't know.
So at the next stop sign (which I usually (cautiously)) blow through, I edged over and stopped and looked at him real meanlike. He screamed GET OFF THE F***ING ROAD and sped off. I caught up to him quickly and was about to pass him between him and the parked cars when he lurched his beemer over to try to squeeze me into a parked car. Had to slam the brakes and REALLY ALMOST got smashed into a parked car. He speeds off again.
Now I am really angry.
(side note) This is a long two lane residential street with cars parked on either side of traffic and many many four way stop signs.
So I caught up to him quickly again. Went to pass on the right and he started to try to swerve right AGAIN to slam me to the parked cars. I spun left, had my keys out, passed on the left and keyed the living hell out of his shiny new beemer as I passed. Row of stopped cars in front of him, nowhere for him to go, he revved up cursing and rear ended the guy in front of him really badly. He got out screaming trying to chase me, but had no chance.
I was gone. I felt really good about it at the time, and laughed quite a bit the rest of the way home.

I would never do something like that again. I was young and angsty and stupid.
It's just not worth it. Who knows what someone could do to you? What if he had a gun? Did he hurt that guy in front of him?

I feel bad about it now.

edit: Not really. He was, in fact, trying to kill me. Or at the least, hurt me really badly.