MAME, MESS and DOOM on a Digital Camera digita.mame.net
Some models of digital cameras are running a special development environment called the "Digita OS", which was supposed to allow developers the power to take better pictures and add cool effects. This team of programmers decided to use this OS to port MAME (An Arcade Game Emulator), MESS (A Computer System Emulator) and DOOM (The ID First Person Shooter) to the camera.

Text-Mode Quake webpages.mr.net/bobz/ttyquake
Bob Zimbinski wired a graphics-to-text library for Linux into the publically-released source code for Quake, and then threw it out into the world. Includes screenshots.

Doom as a Tool for System Administration www.cs.unm.edu/~dlchao/flake/doom
What if you could keep track of your processes by running around in a game of Doom, shooting/wounding soldiers representing processes to reset them, and killing them to, well, kill them? This computing student made a proof of concept.

Automatic Master Lock Unlocker Robot vv.carleton.ca/~neil/robotics/locraker.html
Neil designed and built a robot that can brute-force a Master Combination lock by exploiting weaknesses in how the lock is designed. It can get through any lock in an hour or less.