Desktop Graffitist

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/vandalism et cetera).

http://www.roggel.com/NGNeer/DesktopGraffitist/index.shtml

Windentify

Windentify Beta Lite is a freeware demo of a state-of-the-art voice-based identification system that prevents any sort of unauthorized access to your PC. Secure, reliable, and with the unique facility to restrict access to systems and files to just a single user’s voiceprint, this is the best in voice-based security applications.

http://www.research-lab.com/speech/windentify/windentify.htm