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 role playing game involving a Ringworld, you playing prisoners, and... Zombies! You can download the 24-hour version for free here, and start playing straight away - all you need is one to four players, a deck of cards and these rules. Prefab heroes provided, play while you read.
WARNING - CONFINED SPACE - NO SURVIVAL GUARANTEED