The Prank: If you don't mind dropping a few bucks, you can grab some gadgets that'll take your intraoffice pranking to completely new levels. We're talking random beeping, buzzing, and keystroke magic -- things that, in my mind, are well worth 10 bucks.
The Process: I can personally recommend ThinkGeek's Annoy-a-tron, currently $9.99; Annoy-a-tron 2.0, $12.99; and Phantom Keystroker v2, $12.99. Any of those will provide you with hours of joking joy.
The Final Product: The Annoy-a-tron is a tiny and almost unnoticeable magnetized chip that makes obnoxious beeping noises at random intervals. You set the frequency of the beep (higher pitch = higher annoyance potential), then hide it anywhere you want -- under someone's desk, on the back of a computer, you name it. The Annoy-a-tron 2.0 adds an optional IM doorbell noise or super-high-pitched tone that only teens can hear.
The Phantom Keystroker puts a different twist on gadget-induced insanity: The device, which looks like a USB thumb drive, sends random commands when plugged into a computer. You can set it to make mouse movements, type random letters, or even just toggle the caps-lock from time to time.