Purdue Technology students build supersonic ping pong gun

Purdue College of Technology professor Mark French tasked his doctoral students to realize his vision for the world's first supersonic ping pong gun. Their air-powered Bazooka launches the inefficient ammunition at Mach 1.23, faster than an F-16 fighter jet. Despite their lack of mass, the featherweight balls pack a lot of energy.
http://www.purdue.edu/newsroom/releases/2013/Q1/supersonic-pingpong-bazooka-blasts-balls-at-mach-1.23.html