USR (Unbelievably Simple Role-playing)

From the introduction:

Have you ever fancied yourself as a space-faring adventurer, exploring the vast regions of an alien-filled galaxy? Or what about a master sleuth in Victorian England? Perhaps you want to live out the exploits of a thief in a fantasy realm? With the USR system you can do all this and more. Using the simple rules in this booklet, you will soon be creating exciting stories with your friends while munching on high-carb snacks.

USR is an easy game to learn but there are optional rules throughout if you fancy making it a bit more advanced. Feel free to add your own rules or change current ones to match your preferences. The most important thing is that you and your group have fun with it.