the cop lives down my block and i was getting my mail and all of a sudden this cop comes barreling out of this alley with flashing lights and the kid in the car slammed his hands on his dash and i just laughed.
This one is my favorite. I also like the "point and laugh suggestion" but if you are asking the devil in me see below
Cut a single front brake line with a pair of snips so that he has a small leak. Avoid this one though as the accident could result in the harm of a third party.
Get some shatter rock and break out all of his windows. This is very expensive for him but he will still have his car.
Buy a full container or two of bbq lighter fluid, use a piece of shatter rock or a center punch and break out the small window, proceed to douse the seats with the fuel and once it is all gone lighter up. This is my favorite and don't worry cars don't really explode like on TV, the pow you will hear will be the tires popping.
All are illegal, all cause significant damage and all are things that must be fixed (if he can fix it) before he can use the car again.
soak a rag in oil/gasoline/lighter fluid ( something flammable )
wrap it in tin foil and tap a firecraker to it
when he drives buy light the firecracker and throw it in his window, when it pops it will disintegrate the tin foil and ignite the rag setting his whole shit on fire