FlyingDog

If the cops won't help and you don't want to damage the other guys vehicle, try this. You have the license plate number and can get his address obviously if he's going to be receiving a letter from a law firm. Go fill his exhaust with spray foam insulation. Just use enough to clog it, but not come out the back. It won't damage anything, but he'll spend a ton of money trying to figure out what's wrong.

Along the lines of Gretch's idea... I hear dog crap in the exhaust makes some horrid long lasting stink.

Ron_H

sublimate

When I was in high school there were all sorts of car "pranks" people would pull:
1. If the car was unlocked someone would wedge a stick between the seat and the horn and then lock the doors (sometimes with more twigs jammed in the locks, sometime with dog crap on the door handles).
2. If the car was locked they'd slide sardines between the windows and weatherstrip down into the doors. And if the windows were open a crack they'd squirt milk inside. After all day in the hot sun it would reek more than you can believe.
3. One of the funniest pranks happened when we were away at a rival school for a game. When the bus got back to our school late that night someone (we never found out who) had taken a floor jack and used it to move all our cars so they were so jammed up that it took hours to get them out of the lot. There was no damage, but they were all wedged sideways, backwards, between walls and other cars, bumpers right up against doors where you couldn't even get into the cars you needed to move. One car was sideways in the entrance where it fit with less an inch at either end and there was no way to drive it out (luckily there were enough of us to lift/scoot it out).

SharkSkin

Here's a little trick for 4-door cars:

Get a piece of stout rope, and use it to tie the front door armrests tightly together. Leave by the rear doors, locking them. It was a lot more effective back in the day before every car had power locks...

H2

I'm surprised someone didn't mention attaching a logging chain to the offender's rig's rear suspension..then to a tree...or fire hydrant. Not suggesting this...but I remember it happening in Tennessee when I just a young pup. Some revenge probably gets sweet enough to get you jailed in today's world. I'd just report a "hit and run" to the cops as has been suggested....if you've got a camera showing the perp's rig...that's even better.

h2