We couldn't get a quorum for our regular D&D game, so instead my son ran a one shot (pun intended) western using Sidewinder Recoiled with a few mods. The outing was based on the movie, "The Quick and the Dead". We rolled up characters (being a d20 game it always takes longer than we expect - so many fun choices) and off we went. We had no idea in advance what the adventure was, so our characters were not optimized for the adventure.
Like any good western there was a bar room brawl, gun fights in the street, and the big shoot out finale which included a bad guy getting shot dead and falling off the roof. Two of the characters entered the gun fight contest, because, what the heck, it was the adventure. Surprisingly, my character, the River City Kid, made it all the way to the final round to go up against the mayor (who looked strangely like Gene Hackman). The mayor changes the rules 15 minutes before the duel (which would indicate certain death for the Kid), and my character decides not to follow his rules any more and all hell breaks loose. Fortunately for the Kid, the other characters come to his aid, risking their lives for cinematic glory. A number of memorable moments by all characters, many of the perfect western classic type lines. In the final scene the dead mayor's Peacemaker is slammed on the bar by the Kid who says to the saloon keeper, "I believe you have my two thousand dollars." Great fun overall.
I don't hesitate to recommend Sidewinder Recoiled as a fine d20 western implementation. It is really easy to run if you already know d20, and has some nice elements to make it western specific.
The only thing we didn't do was head them off at the pass. Maybe next time. The dice never lie.