Before it collapsed due to schedule conflicts, I briefly ran a game based on the anime/manga Trigun. (taking the best of both)
Almost 200 years ago humans crash landed on a dustball planet, civilization is rebuilding. Society has regressed to a wild west type stage where might makes right and outlaws roam the badlands. It was pretty fun, but I never actually managed to get into my main plot (the resurrection of the Gung-Ho Guns under the leadership of the third walking plant.)