Update: Ringworld Zombie is now available with all new artwork, as a print-on-demand high quality card deck from DriveThruCards. It's most fun with three or four players, but you can play solo too!
According to Rob Lang I now probably deserve a place in the special padded room for those who could not resist doing two 24-hour RPGs for the same competition. Yet, here is my second one:
RINGWORLD Z O M B I E
It's a fast, fully illustrated, game-masterless card game (and a simple role playing game) involving a Ringworld, you playing prisoners, and... Zombies!
You can order the game from DriveThruCards here. Rules are on the cards, and/or a free pdf ruleset can be downloaded from here.
WARNING - CONFINED SPACE - NO SURVIVAL GUARANTEED