During the opening 1987 sequence, a young Matty Demaret (Andrew Francis) is given a third-generation Colt Detective Special by his uncle Teddy Deserve (John Malkovich) and is told to execute Bobby Boulevard (Mike Starr) with it. Billy Clueless (Arthur J. Nascarella) later uses a snubnose, possibly the same 3rd generation Colt DS.
Smith & Wesson 5906
Both Sheriff Stan Decker (Tom Noonan) and his deputy Donny Ward (Shawn Doyle) carry Smith & Wesson 5906 pistols in their holsters, each drawing them at various points in the film.
SIG-Sauer P226
Matty Demaret (Barry Pepper) buys a SIG-Sauer P226 from the gun shop in Montana, firing it several times throughout the film.
M1911A1
Taylor Reese (Vin Diesel) uses two M1911A1 pistols, purchased from the Montana gun shop, until the finale. Freddy the Watch (Nicholas Pasco) also uses a 1911, albeit a stainless model.
Beretta 92FS
Johnny Marbles (Seth Green) buys a Beretta 92FS from the gun shop, firing it at the range afterwards.
Since it lacks the sight rin on the top of the slide and slanted cocking serrations, I don't think this is a CGCNM. I'd say it is likely a custom Series 70 like the one in The Mask. - Gunmaster45
double-barreled shotgun
Gordon Brucker (Kevin Gage) enters the standoff with a side-by-side double-barreled shotgun with exposed hammers.