Stick 3 boxes of plastic forks in his yard.
Shred newspapers up, put them in a trashbag, and sprinkle them over the forks.
Or just T.P his house.
Saranwrap his car/house/trees/whatever.
Soap doornobs, vaseline doornobs.
Shaving cream a car.
Bologna + Car = polka-dots
Salt a nasty message into his/her yard. OR, better yet, fertilize a nasty message into his yard.
Jack up his car, take off the wheels, then set the car down on the wheels, and take his spare tire jack.
Buy a valve stem repair tool, and slightly loosen his valve cores, or take them completely out and just put the little plastic cover back on.