Chances are you won't get your money back, as others have said, if there was never a lease agreement or other signed documents you probably won't have much to go on in court.
Also violence (i.e. kneecapping him) would probably be pretty satisfying, but would probably just result in a shit-ton of legal problems for you.
If you just want to screw with him and cost him some money and headaches, you could screw with his car. Contrary to popular belief sugar in the tank does nothing, however I believe that putting a fair amount of bleach (like a gallon) into his gas tank will cause a LOT of problems, especially if it sits in there for a while and then gets pulled into the engine. Apparently adding it to the oil pan does wonders as well, but would probably be hard to get into the engine without breaking into the car.
Keep in mind, that this is HIGHLY illegal, but would be a lower risk method of screwing with him compared to going all 'Tonya Harding' on his ass.