The issued sidearm of the FBI Special Agent Audrey Parker (Emily Rose) is SIG Sauer P226. It's also used by the other woman who identifies herself as FBI Special Agent Audrey Parker.
Glock 17
Third generation Glock 17 is the standard issued sidearm of Haven Police Department. It's used by Detective Nathan Wuornos and later by Detective Audrey Parker.
Smith & Wesson model 36
A nickel plated Smith & Wesson model 36 is found on a crime scene in the first episode. It is also the sidearm of the chief Garland Wournos.
Heckler & Koch USP
A thug in episode 11 carries Heckler & Koch USP with stainless steel slide.
Smith & Wesson 5906
Another thug in episode 11 carries Smith & Wesson 5906. It's later used by Duke Crocker.
Remington 870
Duke Crocker uses Remington 870 in episode 13 to protect himself from Max Hansen.