Carnage is a free role-playing game written by a guy named Joe Byrd.
The main advantages the system boasts are an incredible degree of lethality, almost similar to that of Shadowrun, and an incredible degree of freedom in characters you can create with it. It's completely generic, although according to the changelog, a setting is due in the next edition.
- It's d6-based, with exploding dice. You'll need a d20 if you use vehicles.
- It seems fairly simple, but is updated pretty regularly.
- You can get it here: http://www.mediafire.com/view/?b9f0u563b15dnpb
- Also from the maker of Carnage: Brutality!
- Get that here: http://www.mediafire.com/view/?lkfa0lblcm3q2gq