Desktop Graffitist is a small program that enables you to spray paint your desktop, and anything else that might appear on screen. DG is designed for recreation and creativity, and can be used to relieve office stress and boredom.
Aside from the added bonus of allowing you to vent on that stupid monthly report or the latest homework assignment, the program is also good for leaving messages on other people's computers that they can't miss (love notes, hate notes, grocery lists and art/graffiti/vandalism, ...).
Simply run it and use your mouse to paint all over the desktop. The right button changes color, the ESC key wipes off the screen. It's simple, relaxing, addictive, free, and totally fun!