A Smith & Wesson Model 15 is briefly seen holstered on a USAF airman in the Minuteman II Oscar-1 Launch Control Center at Whiteman AFB in Missouri. This footage is actually taken from a 1979 documentary called First Strike.
Remington 700
Remington 700s are seen in the truck Stephen Klein (Steve Guttenberg) gets into as he hitchhikes back to Joplin, Missouri. They are also used by militia to execute looters.
Ithaca 37
Ithaca 37s are seen being used by US National Guardsmen defending the aid truck.
MGC M-16
The MGC M16 replica is utilized by US Air Force Security Police at the Oscar-1 Launch Control Facility and later by US National Guardsmen.
After a fight breaks out at a water pump a man draws his Colt Lightning to break up the fight so Airman McCoy (William Allen Young) and "Cody" (Bob Meister) can have a drink.
Combination gun
A Combination gun is seen briefly being carried by a farmer at the farmer's meeting.
Over & Under shotgun
Jim Dahlberg gives Steve Klein an Over & Under shotgun when he takes Jim's daughter Denise Dahlberg and Danny Dahlberg to the hospital in Lawrence.
Side by Side shotgun
A wastelander kills Jim Dahlberg with a double-barreled shotgun when he asks them what they are doing there.
Trivia
Due to the studio being denied footage by the DoD (the studio opted to make who attacked whom first ambiguous rather than depicting the Soviets as the aggressors, defying the DoD's request), the mushroom clouds in the film were made by injecting colored ink plumes into a water tank.