How about....a grappling cannon?
If u hav seen 2fast 2furious you should know what i mean....its the things the police in the chopper fired at them when they were speading, and he pulled it out the side of the car? ;D Like a massive Triple hook on a line. They take down choppers, cars and so on. I think the one in 2f2f was a grappler but i dont think a grappler drawn the power from a car/shuts a car down. It would be cool fired from a tank or ship or sumthing, or even a purpose built car like a scud, but with a massive cannon instead of a rocket!
Any ideas/help?