That's what I'm talk'in about: Supersonic Ping Pong ball gun

The warning at the end of this clip, by Purdue University professor Mark French, is "Do not try this at home." Yeah, right.

French and his ME students are demonstrating a de Laval nozzle using a Ping Pong ball. They launch the thing at supersonic speeds and, in so doing, impart enough force to blow a hole through a conventional Ping Pong paddle.

The paper describing their work is here: http://arxiv.org/ftp/arxiv/papers/1301/1301.5188.pdf