The following guns were used in the film Fight Club:
Smith & Wesson 4506
In the opening sequence and at the end of the film, Tyler Durden (Brad Pitt) holds an older-model Smith & Wesson 4506 (recognizable by its squared trigger guard and frame bulges) in the "Narrator's" (Edward Norton) mouth. This was the gun the "Narrator" took from the detectives that were questioning him. It is noted as a 4506 by its rounded butt and its wraparound grips, as opposed to the non-wraparound grips and the straight butt of the Smith & Wesson 645.
Tyler Durden pulls a Colt Python out of the Narrator's bag before going to the "human sacrifice" in the store. At the end of the movie, the Python is also seen in the hands of The Mechanic (Holt McCallany).
In one scene, the owner of the bar (named "Lou's") which holds a fight club event is disrupted by Lou himself. Lou's large bodyguard (Carl Ciarfalio) is armed with a SIG-Sauer P226, which is only seen clearly very briefly.
Again very briefly seen, a police officer fires a Beretta 92FS at Big Bob after "Operation: Latte Thunder" goes disastrously wrong.
Thought one is not seen on screen, The Narrator (Edward Norton) intimidates his boss with the threat to "... stalk from office to office with an Armalite AR-10 gas-powered semi-automatic carbine, pumping round after round into colleagues and co-workers." after his boss finds a copy of the Fight Club rules in the copier machine.