Larry Vickers demonstrates the FN P90 personal defense weapon

The P90 is the ultimate system for operating in MOUT/urban and other close-quarter battle scenarios and is built around FN’s revolutionary 5.7x28mm ammunition.

A compact 50-round box magazine runs horizontally along the top of the P90. Empty cases are ejected downward where they cannot interfere with the operator. The P90 fires from a closed bolt, giving it outstanding accuracy and making it easy to keep rounds on target. It is the ideal personal defense weapon for armored vehicle or helicopter crews, executive protection, law enforcement and tactical entry teams.

The P90 is currently being used by the US Federal Protective services.

http://www.fnhusa.com/mil/products/firearms/family.asp?fid=FNF012&gid=FNG007