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.
Mossberg 500
Elwood (Ethan Suplee) trades his Mossberg 590 shotgun for the more traditional Mossberg 500 shotgun (which is seen again later in full, showing it has an extended magazine tube). Sheriff Briggs (Ray Baker) is also seen using the Mossberg 500 later, showing off its extended magazine tube, when he meets up with Elwood and Dennis at the end of the film. At first glance it appeared to be a Winchester 1300 shotgun, but a closer look at the location of the safety shows it is a Mossberg 500.
L1A1
Dennis (Abraham Benrubi) uses an L1A1 inch pattern rifle with a laser scope as his weapon of choice throughout the film. The rifle has a custom flash hider not usually attached to the L1A1. The inch pattern is evident by the front sight and the rear sight as well as details in the upper receiver and pattern of the foregrips.
M16A1
Elwood later uses an M16A1 rifle, fitted with Cobray 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.
Cobray CM203 37mm Flare Launcher
Elwood's M16A1 is fitted with an Cobray CM203 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 Stainless
Dennis uses a Bereta 92SB with a stainless finish 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, Cimmeron, or Ruger Vaquero copies, or perhaps genuine Colts.
Browning Hi-Power
Dennis is seen briefly holstering a Browning Hi-Power but it is never seen again.
Grenade
An unknown grenade is used by Elwood, who drops it when Dan knocks him and Dennis into the mine shaft. Jerry (Matthew Lillard) picks it up and manages to luckily take out the three bad guys when the grenade blows up a tree, falling on them just in time. It is possibley a cigarette lighter.