A suppressed Beretta M1934 was used by Rizzo Mob Liuetenant Anthony "Red" Cervelli (James Russo) in "(Ill)Legitimate" (S1E04).
Browning Hi-Power
A home invasion robber uses a nickel plated Hi-Power in "All That Glitter" (S1E03). Assassins working for the Milwaukee Mob fire Hi-Powers at Savino at a parking garage in "(Ill)Legitimate" (S1E04). Jones (Damon Herriman), a mob enforcer for the Milwaukee Mob, is armed with a nickel plated Browning Hi-Power in "Solid Citizens" (S1E05). Rizzo Mob enforcer Vic Borelli (Joe Sabatino) uses one in "The Real Thing" (S1E06). Johnny Rizzo (Michael Wiseman) uses a Hi-Power when confronting Jack Lamb (Jason O'Mara) towards the end of "Road Trip" (S1E13), Jack gets a hold of it after Rizzo is stabbed by a junkie and kills him.
Colt Model 1903
A suppressed Colt Model 1903 is used by Borelli in "(Ill)Legitimate" (S1E04).
Colt M1911
Air Police officers uses the Colt M1911 as their main sidearm.
CZ 52
A CZ 52 was used by Jones (Damon Herriman) in "Bad Seeds" (S1E07) as his weapon of choice.
Walther PPK
Las Vegas Assistant District Attorney Katherine O'Connell (Carrie-Anne Moss) uses a nickel-plated Walther PPK with wood grips as her personal sidearm, drawing it on Savino (Michael Chiklis) when he threatens her in "From This Day Forward" (S1E12) and using it to fire at the fleeing Jones in "Road Trip" (S1E13).
Unknown
Revolvers
Colt Detective Special (1st Generation)
Red uses a 1st Generation Colt Detective Special as his main sidearm, first seen in "Bad Seeds" (S1E07). A corrupt USAF OSI investigator fires one at Lamb's truck during the chase near the end of "Exposure" (S1E08), it was loaded with hollow points which were used to kill an Air Force doctor at the beginning of the episode. Jack Lamb (Jason O'Mara) carries a Detective Special, it can be seen holstered on his belt and is taken by Rizzo (Michael Wiseman) in "Road Trip" (S1E13), who attempts to draw it after his Hi-Power is dropped, Jack takes the Colt from Rizzo's hand before leaving the scene in "The Third Man" (S1E14).
Colt Detective Special (3rd Gen)
A 3rd Generation Colt Detective Special is seen in the possession of a murder suspect in "Pilot". Sheriff Ralph Lamb (Dennis Quaid) is later seen with the revolver, the presence of a 3rd Generation Detective Special is an anachronism due to the fact that the show takes place in 1960 and the 3rd Gen DS came out in 1972.
Smith & Wesson Model 10
A Smith & Wesson Model 10 is pulled by the Clark County Sheriff in "Pilot" (S1E01). Clark County Deputy Sheriffs are also armed with the Model 10. A Model 10 is found by Ralph during a search in "All That Glitter" (S1E03). It would appear that Sheriff Lamb (Dennis Quaid) also uses a Model 10 as his main sideaerm. Ralph cleans the Model 10 in "(Il)Legitimate" and is first used in "Solid Citizens" (S1E05). Savoy Casino guards are armed with Model 10s in "The Real Thing" (S1E06).
Smith & Wesson Model 19 Snub Nose
Vincent Savino (Michael Chiklis) uses a nickel 2.5" Smith & Wesson Model 19 as his personal sidearm. He first uses it when confronting Jesse Lynch (Alex Nesic) in his trailer at the end of "The Real Thing" (S1E06).
Smith & Wesson Model 36 "Chiefs Special"
A Smith & Wesson Model 36 "Chiefs Special" is used by Ginny Merrick (Melinda Page Hamilton) to fend off the Lamb brothers after knocking on the Merrick apartment in "Estinto" (S1E10).
Unknown
Shotguns
Ithaca 37
The Ithaca 37 shotgun is seen carried by Ralph's son Dixon (Taylor Handley). A jewel store robber uses one with a pistol grip before Ralph and Jack apprehended him in an ambush in "Money Plays" (S1E02). The same weapon was also used by a home invasion robber in the same episode. Two men who hijack the ambulance transporting the dead USAF doctor's body in "Exposure" (S1E08) use Ithaca 37s. A sawed off Ithaca 37 is used by Nathan Auster (Stephen Taylor) in "Paiutes" (S1E11).
The Winchester Model 1912 is one of the firearms owned by Ralph Lamb (Dennis Quaid). Don Simmons (Gill Birmingham) uses the 1912 in "Solid Citizens" (S1E05). Dixon uses one in "The Real Thing" (S1E06).
Air Police officers were armed with M1 Carbines as their main weapon.
M2 Carbine
Kidnappers are armed with M2 Carbines in "Solid Citizens" (S1E05).
M14
What appears to be an M14 is briefly seen carried by an MP when a murder victim is found in "Pilot" (S1E01).
Winchester Model 1894
The Winchester Model 1894 rifle is one of the firearms used by Sheriff Ralph Lamb (Dennis Quaid). Ralph's brother Jack Lamb (Jason O'Mara) also is seen with the rifle. Savino uses it one in "Bad Seeds" (S1E07) after Milwaukee mobsters led by Jones invade the Lamb ranch at the outskirts of Las Vegas. Majority of the armed Mormons in "Paiutes" (S1E11) are armed with 1894s.
Others
Molotov Cocktail
An arsonist hurls a molotov cocktail in an attack on the Tumbleweed Casino in "(Il)Legitimate" (S1E04).