Elwood (Ethan Suplee) wields a Mossberg 590 shotgun in the scene where the boys stumble upon he and Dennis' pot field, he fires several shots, missing the fleeing boys.
Dennis (Abraham Benrubi) uses an FN FAL full stock rifle with a laser scope as his weapon of choice throughout the film.
M16A1
Elwood later uses an M16A1 rifle, fitted with Colt 37mm Flare Launcher. Towards the end of the film, Dan (Seth Green) picks up Elwood's M16A1 but shows his lack of experiance as it fires wildly.
Colt 37mm Flare Launcher
Elwood's M16A1 is fitted with an Colt Flare Launcher 37mm in place of the HE M203 grenade launcher, though he never fires it.
Beretta 92SB
Elwood uses a blued Beretta 92SB as his sidearm, as noted by the rounded trigger guard. The county police are seen with 92SBs in their holsters as well. (They are assumed 92SBs because why buy another gun if you don't even see it?)
Beretta 92SB INOX
Dennis uses a Bereta 92SB INOX stainless finish model as his sidearm, also featturing a rounded trigger guard.
M60E1
Elwood loads up an M60E1 machine gun and uses it with great effect to destroy most of Del Knox's (Burt Reynolds) house.
Unknown Double Barrel shotgun
Del Knox (Burt Reynolds) uses an unknown double barrel shotgun to force the boys to his house and keep them from running.
Colt Single Action Army
Del Knox (Burt Reynolds) keeps two Colt Single Action Armies in cross draw holsters. He uses them to blow up Dennis and Elwood's ATv, stopping the assault. He fans them from both the left and right hands, holding 5 shots in each, A well know safety precaution with old six shots. Load 5 bullets and drop the hammer on an empty chamber. They are only briefly seen and could be Uberti or Rufer Vaquero copies, or perhaps genuine Colts.