Fistfull of Frags is a HL2 western theme modification.
It contains many popular weapons such as the colt peacemaker, and henry rifle.
If you have HL2 then you can play this game.
Its online, and is tons of fun.
Currently their website is down but you can download the game at:
http://www.fistful-of-frags.com/

Also please watch the video I made showing all the fancy weapons.
http://www.youtube.com/watch?v=WFwG6bXDpYg