Turn off the power to his house.
Get sand bags and stack up infront of his front door to house.
They use to have these smoke bombs you put under the hood of a car, when they drive or start the car, it goes boom and makes lots of smoke.
Put holes into his socks.
Change the numbers for his address on his house.
Install remote control light switch to one of his house lights and control from outside or whatnot.
If he has one of those pull-out sprayers for his kitchen sink, use a rubber band and tie it down so whenever he turns on the water, it'll spray him.
Tape some bubble wrap under the floormat to his front door.
Put some bubble wrap under the car tires.
Frost all his windows with fake snow stuff.
Reverse the hot and cold water to one of his faucets.
Cake him when he blows out the candles on the cake.
Silly string is always fun.
I'm sure theres more...just can't really think of much.