The Single Action Army revolver is the main firearm seen in the film. Roy O'Bannon (Owen Wilson) carries a pair of Colt Single Action Army Quick Draw revolvers with custom pearl grips for the majority of the movie. He later is seen teaching Chon Wang (Jackie Chan) on how to use it. Marshal Nathan Van Cleef (Xander Berkeley) also carries dual SAA's.
Single Action Army (Artillery Model - 5.5" barrel)
After his Single Action Army pistols are taken away by Marshal Van Cleef, Roy can be seen using a Smith & Wesson Schofield in conjunction with Lo Fong's Chamelot-Delvigne 1873 during the church shootout.
Several different models of the 12 Gauge Double Barreled Shotgun are used in the film. Blue, one of Wallace's goons, carries a sawed-off double barrel as his weapon of choice and is seen using it during the opening train robbery. When Roy and Chon get into a bar fight, the local sheriff fires his double barrel into the ceiling to break it up. Falling Leaves (Brandon Merrill) also used one to spook cattle as she breaks Roy and Chon out of a local jail.
Henry 1860
Falling Leaves (Brandon Merrill), the Native American wife of Chon Wang (Jackie Chan), can be seen using a Henry 1860 rifle (as identified by the way she loads it by rotating the end of the gun to expose the tubular magazine) during the rescue of Chong and Roy at the Gallows.
Remington Rolling Block Pistol
At the beginning of the film, Andrews (Jason Connery), the man who brought Princess Pei Pei (Lucy Liu) to America, pulls what appears to be a Remington Rolling Block Cavalry single shot pistol as he threatens Lo Fong.