Used my bike once to keep a punk in his friends car. He was about 1/2 second away from me breaking out one of his windows (one of the reason's I like bar extenders)
One night I was riding home in a bike lane when a car full of Asshats pulls alongside and startle honks me, then the passenger starts yelling and threw something out the window at me (hard, not a casual toss). The geniuses then get caught at the next intersection about (1/2 block away) by a red light with a car stopped in front of them. I come up, yelling, and trying to take down the license plate before I call it in to 911. Passenger punk starts to try to get out of the car, but I used my bike to keep the door from opening, all the while attracting the attention of the vehicles coming up behind them and alongside.
Dude rolls down the window to tried and punch me. Had I gotten a chance, I would have grabbed his arm and pulled it in a direction opposite the joint, hard (I wanted to hear the sound of breaking bone(his,not mine)). At that moment, the light changed, and his buddy drove off. Had I had his arm, I would have kept holding it to make sure of maximum damage. I'm certain that my pedal left a nice gouge along the the passenger side body work. With the car gone, I stood clear of the intersection, busy trying to call the cops.
The driver behind them witnessed the incident, and followed them and wrote down the license for me, then circled back, found me, and gave it to me.
Unfortunately, the cops weren't able to catch the driver on the road, but they did go to the address associated with the car. That was all I heard from them. I can only imagine what Asshat's dad thought about this situation, having the cops come along to tell them about it and a nice bit of paint missing down the passenger side.