Every working member of the robbery crew was armed with one Smith & Wesson 659 9mm pistol. They are distinguished from 1911 and other Smith & Wesson variants by their second generation features, stainless steel construction, and double stack frames. Though all of the guns look to be the same, Mr. Orange's (Tim Roth) has a round trigger guard and a black magazine, further alluding to the fact that he is not like the rest of the thieves.
Smith & Wesson Model 639
Though everyone is given a Smith & Wesson Model 659 for the robbery, Mr. White (Harvey Keitel) is seen using a Smith & Wesson Model 639 with Pachmayr grips most of the time. We can assume, being that he is a professional thief, that this is his personal gun, and not a continuity error in the film. During the getaway, he is seen dual wielding his personal Smith & Wesson Model 639 with his issued Smith & Wesson Model 659, further strengthening this theory. In the special edition DVD, on the second disk a deleted scene can be found which briefly shows Mr White's/Larry Dimmick's police record. This informs us that his weapon of choice is a Smith and Wesson 9mm, even further strengthening the personal 639 theory.
Beretta Jetfire
Mr.Orange, packs 2 handguns while getting ready to meet Eddie and Mr. White for a meeting with Joe. The automatic he holsters on his ankle is a Beretta Jetfire in .25 ACP.
Charter Arms Off Duty
Mr. Orange's second gun is a Charter Arms Off Duty with Pachmayr grips. He checks to make sure the cylinder is loaded, swings the cylinder back in, and then places it in his coat pocket.
Colt Detective Special
After Mr. White kills the pursuing cops with his two pistols, he and Mr. Orange walk until they find a car driving by. They aim their guns at the driver, a woman, and attempt to take it. She produces a pre-1972 nickel plated Colt Detective Special from her glove compartment and shoots Mr. Orange in the stomach as he opens the door to pull her out of the car. Another Detective Special is "Mexican carried" by Joe (Lawrence Tierney), distinguished as a Detective Special by it's round edged butt.
Smith & Wesson Model 66 Snub Nose
In the final standoff between Eddie (Chris Penn), Joe, and Mr. White, Eddie aims his Smith & Wesson Model 66 Snub Nose at Mr. White, threatening to kill him if he doesn't take his gun off of Joe.
Smith & Wesson Model 19 Revolvers
The police officers in the scene where Mr. Pink is being chased all carrying Smith & Wesson Model 19 revolvers, the only one clear enough to be seen has S&W style sights, but the particular model cannot be distinguished.