Frankengame

From the Game's Introduction:

Frankengame is a 24-hour role-playing game. It was conceived, designed, developed and published in a single 24-hour timeframe.

The GM will describe the setting. There are several rough suggestions for a setting in the Frank's House section (see below). But the GM will need to flesh out the setting as necessary.

The players will create horrible mutants, or fiendishly warped demons, or corpses stitched together and given life by electricity. The point is that all the player characters will have traits and characteristics from several different sources.

Frankengame is best used for a "one-off" game session instead of a campaign, but you can make of it what you will.