This is the greatest office prank, especially if someone's got a computer where the USB port is not evident right away. It will seem as if there is a ghost on their computer... toggling the caps lock or typing random keys. Just avoid doing this on your boss' computer before a big presentation.

The Phantom Keystroker may look like a harmless usb thumb drive, but it's actually a devious contraption of unlimited office-based torture. Simply discreetly attach the Phantom Keystroker to any extra USB port on your victim's computer, no drivers needed.

The Keystroker emulates a keyboard and mouse and periodically makes random mouse movements, toggles caps-lock and types out odd garbage text and phrases. Switches on the side allow you to choose between keyboard garbage typing, caps lock-toggle, annoying mouse movements or all three. An adjustment dial sets the duration between "events". We recommend you don't set it too frequently so as to extend the agony. Your hapless co-worker pal will think his computer has been possessed or infected by a destructive virus. As he writhes in anger and furiously dials tech support you can rest easy with a job well done. (via Think Geek)