My friends and I have always had a fondness for "forking" people. This basically involves sneaking over to their houses at night and placing a few plastic forks in their front yard (usually about 20-40). This is done by sticking the handle end into the ground, with the prongs and some of the handle still sticking up. We decided that this would be a good Senior Class prank, but on a much larger scale...
We gathered at a local billiards hall at about 11 pm. The police in our town tend to be a bit anal, so we knew we'd have to be stealthy. We had each put in about five dollars toward a box of forks, and we put them in backpacks, aprons, and pockets and piled into one person's car. That person would drop us off and circle around and come back in five to ten minutes. We did this several times and an hour and a half (and fifteen hundred forks) later, the entire front lawn was covered. It was fantastic. The next day at school, they made the kids with in-house detention clean them up. It was hilarious.