Clyde Barrow (Warren Beatty) is seen using a Colt New Service multiple times, most notably while robbing the grocery store and when shooting the gun from Frank Hamer's hand. Frank Hamer (Denver Pyle) himself carries a New Service as a Texas Ranger. Buck Barrow (Gene Hackman) carries a New Service during a bank robbery and the Platte City shootout.
Colt Official Police
C.W. Moss (Michael J. Pollard) carries a Colt Official Police revolver, using it during the gang's shootouts. It is this gun that, tucked into his waistband, tips off a policeman in Platte City.
M1911A1
Clyde Barrow (Warren Beatty) uses a M1911A1 during the gang's biggest bank robbery. He does not fire it.
Smith & Wesson Model 10
Clyde Barrow (Warren Beatty) shows off his Smith & Wesson Model 10 early in the film to impress Bonnie Parker (Faye Dunaway), then uses it to shoot bottles off of a fence, giving it to Bonnie to shoot a tire. She also uses one with pearl grips later, as Clyde tells her a Smith & Wesson fits better in her hand, during the bank robberies. Clyde also gives one to the sharecropper and his helper, Davis, to fire at their repossessed house when Bonnie tells them "We rob banks." Buck (Gene Hackman) briefly uses one to subdue Frank Hamer. Several policemen also use Model 10s during the course of the film.
Thompson M1928
A Thompson M1928 is used by the Barrow Gang during the Platte City motor court shootout by Clyde (Warren Beatty), Bonnie (Faye Dunaway), and C.W. Moss (Michael J. Pollard. Frank Hamer (Denver Pyle) and his deputies also use Thompsons when mowing down Bonnie and Clyde in the finale. (The movie depicts this firearm being the Barrow Gang's weapon of choice, but the real Clyde preferred the Browning Automatic Rifle to the Thompson).
Winchester Model 1894
A police officer in Joplin and a vigilante in Iowa use Winchester Model 1894 rifles.