It's Doom 2 running on a TI-Nspire CX graphing calculator... in color!
Are you sitting in Geometry class bored out of your mind, and all you can pull out of your pocket is a TI-Nspire CX graphing calculator? You're in luck, as TI Planet now offers a Doom 2 port, nDoom 2 Final, that actually runs the classic game in full color. That's right: instead of pushing in heavy numbers during an exam, you can shoot loads of buckshot into zombies and Imps, just don't let the teacher catch you.
Hack A Day reports that the game originally appeared in beta form a year ago, running in black and white on a hacked TI-83. Since then, several versions have been released, tweaking the controls and adding a menu system which switches out the menu seen in the original DOS-based retail version.
This specific release also adds the Ndless 3.1 program which unlocks the calculator's hardware, allowing users to perform their own hacks. Sound, unfortunately, still isn't present in nDoom 2, so don't let the video demo pasted below fool you.