umm, i guess it depends how much you want to mess with him. if he has a car its a good place to start. you could glue a condom over the tailpipe, break the valve cores on his tires so they go flat, if you have good access to it, and some car knowledge you can wire the horn into the brake light circuit, so his horn goes whenever he hits the brakes. if you wanna really fuck it up, pour sugar, sand, honey, or other stuff in his gas tank, and if you want to wreck it, you can always light thermite on the top of the hood. if you can get into his house, you could microwave dog (or human) shit, it smells terrible, or put eggs under his sheets, or pee in his mouthwash, or add kool-ade powder to his laundry detergent (make sure its the same color, it will stain all of his clothes). otherwise icy hot in the boxers, laxatives in everything, crushed up tracer pills in his food (they turn your shit bright colors for a few days). these are just a few things, hope some of them work for you.
When Hell freezes over, i'll ski there.