As previously noted, we're setting up new shelving around the Kitten Farm, including a Skandia entertainment center. We can buy shelves faster than we can get them set up, though. For the last few days we've had a 6"-12" stack of disassembled shelves in our dining room. These shelves are a little under two feet square, relatively lightweight, with a smooth finish on both sides.
So, time for Saturday morning Cat Fu practice. Whitey and Billy are chasing each other around the downstairs with wild abandon. Billy runs behind the stack of shelves. Whitey launches himself onto the top of the stack... transferring all his momentum to the low-friction interface between the top shelf and the one underneath. The shelf keeps going, with him on board.
In other words, our little engineering kitten figured out how to throw a shelf at his brother.
Billy got out of the way. The shelf landed with a crash. Both cats were unharmed but were last seen watching the shelves with deep suspicion.