The Smith & Wesson Model 10 appears to be the main sidearm carried by members of the Twin Peaks Sheriff's Department, including Sheriff Harry S. Truman (Michael Ontkean), Deputy Tommy "Hawk" Hill (Michael Horse), and Deputy Andy Brennan (Harry Goaz). In "Checkmate" (S2E13), Agent Cooper is seen having to give up a Smith & Wesson Model 10 when he agrees to become a hostage.
A Colt Python is another revolver used by Sheriff Harry S. Truman (Michael Ontkean). Agent Cooper is also seen with the revolver. A stainless Python is also seen in the hands of Andrew Packard (Dan O'Herlihy).
In "On the Wings of Love" (S2E18), Cooper is given what is identified as a Smith & Wesson 1076 by FBI Regional Bureau Chief Gordon Cole (played by film director and series creator David Lynch). Cole describes it as the Bureau's new 10mm sidearm (The FBI used the new sidearms in the early 90's before it encountered field problems and was replaced). While the prop is referred to as a 1076 in the scene, the weapon is actually an early model Smith & Wesson 4506 given the barrel length, slide mounted decocking/safety lever and double stack step on the frame.
The Walther PP pistol with nickel finish and pearl grips is seen in the hands of Josie Packard (Joan Chen), Shelly Johnson (Mädchen Amick), and Bobby Briggs (Dana Ashbrook) in the series.
In Season 2's "Checkmate" (S2E13), DEA Agent Denise Bryson (David Duchovny) while in disguise is seen concealing a Walther PPK/S in a garter holster. Agent Cooper is subsequently seen taking and using the pistol.
What is later identified by Agent Rosenfield as a "Walther PPK" is seen being used to shoot Agent Cooper.