I vote for dumping a can of pepper spray on him. It may take a while to get the car to a point where you can drive it and not have your eyes water but it would probably make it hard for they guy to finish yanking your stereo. We'd see how things develop after the application of the liquid fire to determine if we take things to the next level. Once you spray the guy, things may escalate quickly so I'd have a firearm in hand and the cops in route.
I'm also partial to the baseball bat accross the shins
