Back in the 1980s, a clever little MS-DOS TSR (Terminate and Stay Resident) program called DRIP would randomly cause on-screen characters to apparently fall from their position on screen to the bottom of the computer screen. It was great fun to install this little program on a victim’s computer and watch them try to repair their documents as letters and numbers would fall at an increasing pace.
Now there’s an annoying product that plugs into a USB port on the victim’s computer. The Phantom Keystroker messes with the user’s keyboard and mouse inputs. Read about it here: http://www.thinkgeek.com/gadgets/electronic/ae83/