For the blocked up car thing, unless your neighbour drives a 4 by everywhere, you only need to jack up the passenger side drive wheel. Th differential won't let his side turn while the other is spinning and he'll never see the gap when he get's out to look.Another car gag is the one where you need access to the inside of the loser's car.
You get one of those flat, ractangular cans of sardines in oil, open just the one end of it, empty the oil out and put it either under the back seat foam or pull away the door panel and put it in there.
One of the funnest gags I've done is to put buillon cube (OXO cubes in the UK) in a victim's shower head. They go around all day smelling like beef or chicken gravy - your choice.
There's also the good old stuff. Vaseline/boot polish on the earpice of the phone.