As mentioned in the OP, bowling balls dropped off buildings are fun!
When in college, we dropped one off a 5 story building (our fraternity house) into our neighbors lawn (another fraternity). It sank into the earth quite a bit.
We had to help fix the damage, of course.
The dormitory (Baker House) near my fraternity used to enjoy dropping piano's off their six or seven story building roof as standard ritual every year. The broken pieces would then be dropped off the Harvard Bridge into the frozen Charles River ... they eventually stopped doing that one, since it could not be cleaned up properly once the ice stopped freezing (due to the bubblers that were installed to remove the pollution in the river).