Every office should have one

http://www.iwantoneofthose.com/search.do?productCode=mislau

The USB Missile Launcher is the ultimate deterrent against those annoying people who lurk around your desk because they've nothing better to do. The Launcher holds three foam missiles, and Missile Command is located on your desktop (which is a great deal more convenient than having it buried under Cheyanne Mountain in Colorado - but that's Norad for you). You simply use your mouse to control the launcher which rotates and tilts as you zero in on your victim, that, despite being deeply childish, is immensely satisfying. The Missile Launcher fires its three foam missiles sequentially as you hit the 'Fire' button, and though collateral damage is minimal, the fun factor is exceedingly high.