Krazy 8 uses a S&W 4506 in "Pilot" (S1E01). Not long after, Walt becomes its new owner before Jesse finally disposes of it in the following episode "Cat's in the Bag…" (S1E02).
Tuco Salamanca (Raymond Cruz) uses a Jericho 941 R with a two-tone finish as his sidearm. In "Grilled" (S2E02), Jesse takes it from him while they are fighting on the ground and uses it to wound him. It is later buried in the desert in the following episode.
What appears to be the Glock 17 is carried by police officers, notably in "Live Free or Die" (S5E01). In "Madrigal" (S5E02), Chris (one of Mike's former men) uses one with a suppressor to kill Duane Chow.
DEA Agent Hank Schrader (Dean Norris) shows off his issue Glock 22 during the party in the first episode. He actually refers to it as a Glock 22 and praises the power of the .40-caliber round over 9x19mm (claiming to have seen the latter cartridge ricochet off a car windshield). He uses the Glock 22 in his shootout with Tuco in "Grilled" (S2E02). It can be seen occasionally throughout season two and three.
Jesse buys and plans to use a Beretta 84F to take revenge on drug dealers who killed his friend, but he never fires it as Walt intervenes with his car. He later pulls the pistol on Gale in Season 3's finale "Full Measure" (S3E13). In "Madrigal" (S5E02), Mike uses a supressed Berettah Cheetah to kill his former man Chris, at the conclusion of the episode he is seen checking it and later threatening the paranoid Madrigal executive Lydia with it.
In "Live Free or Die" (S5E01), Mike pulls a Beretta 92FS Inox on Walt. In "Buyout" (S5E06), Jesse & Mike pick up Beretta 92FS Inox pistols from dead men and use them when escaping Don Eladio's compound, Jesse empties his into a cartel member who wounds Mike.
A Beretta Cougar is held by one of the drug dealers before the shootout in "Half Measures" (S3E12). A Cougar also appears in the hands of a cartel guard in "Full Measure" (S3E13).
A Heckler & Koch Mark 23 is used with a suppressor by Mike Ehrmantraut (Jonathan Banks) in Season 3's finale "Full Measure" (S3E13). The suppressor he uses is a fake "Hollywood suppressor" which screws into the barrel of the pistol (via the threading for the blank adapter), rather than onto the exterior threading. Mike uses the Mark 23 again in "Bullet Points" (S4E04) to take out a pair of Ciudad Juárez cartel gunmen who ambush a refrigerated truck transporting methamphetamine (though he uses it without the suppressor in this episode).
An Colt Woodsman is one of the weapons that Mike disposes of by throwing it into a well in "Say My Name" (S05E07). Although only the front portion of the pistol is seen so it is not possible to positively identified the specific model, the 4.5" barrel, high ramped front sight and the shape o the triger guard suggest it is likely a 2nd series "Sport".
The Ruger KGP-161 appears to be Emilio's gun and is taken out of the yellow bag by Walter and later dissolved in the tub in "Cat's in the Bag…" (S1E02).
The Ruger SP101 is the revolver purchased by Jesse and seen in Season 2's premiere "Seven Thirty-Seven" (S2E01). He uses it to intimidate an unnamed female junkie and her husband, Spooge after they rip-off one of Jesse's dealers. This Ruger also is pulled by Mike in Season 3's finale "Full Measure" (S3E13).
Walter White purchases a Ruger LCR from an illegal arms dealer (Jim Beaver) along with a leather I.W.B. holster in "Thirty-Eight Snub" (S4E02). The arms dealer recommends he load it with 158 grain hollow points for good stopping power, and also recommends he not cross draw unless he is sitting down. Although the Ruger is seen quite a bit in season 4, Walt only successfully uses it once. Walt later retrieves one from the soda machine in the car wash in the episode Confessions, and uses it to search his house for Jesse.
In "Bullet Points" (S4E04), a refrigerated truck guarded by Mike (Jonathan Banks) is ambushed and then shot up by two Ciudad Juárez cartel enforcers, both of whom are armed with Heckler & Koch MP5Ks.
An M4A1 Carbine is used by Tuco (sometimes with an ACOG scope) in Episode 2x02, "Grilled", when he takes Walt and Jesse hostage. Walt later takes this weapon from him when Tuco is bashed over the head with a rock by Jesse. However, Tuco gets it out of the car when DEA agent Hank, who is also Walt's brother-in-law, arrives at Tuco's hideout. DEA agents also use M4A1s when they arrest Jesse in 'Bit By a Dead Bee'. The M4A1 appears again in Episode 4x06, "Cornered" in the hands of one of Gustavo Fring's (Giancarlo Esposito's) gunmen riding in the back of the refrigerated truck.
The other of the two mercenaries guarding the refrigerated truck in Episode 4x06, "Cornered" is armed with a Colt Model 933, the shorter-barreled version of the M4A1 carried by his accomplice.
Clovis, a tow truck and junkyard owner who is a cousin of an associate of Jesse's, uses a shortened Mossberg 500 to threaten an intruder sleeping in Jesse's RV, but put up his gun when the intruder turns out to be Jesse himself (S2E4, "Down"). Specifically, the weapon appears to be a cut down 500AT; the stock has either been shortened to, or replaced with, a pistol grip, but the barrel appears to be original as it has the original bead sight (thereby narrowly escaping being a "short-barreled shotgun" for purposes of the 1934 National Firearms Act).
Walter White (Bryan Cranston) is seen retrieving an M60 machine gun, with an instruction manual and several boxes of ammunition, from the trunk of a car after purchasing it in "Live Free or Die" (S5E01). The machine gun is later seen in the series finale "Felina" (S5E16).
Cartel enforcer Gaff uses an version of the Remington 700 bolt-action rifle with Badger ordnance BDM (Badger Detachable Magazine) bottom metal, and Barrett BORS equipped scope to kill one of Gus's henchmen, and fires several more shots at Gus.
A music video appears in the Season 2 episode "Negro Y Azul" (Spanish for black and blue). A multitude of weapons appear in the video. All of the guns which appear in this video are clearly airsoft weapons, as opposed to the blank-adapted real firearms used elsewhere on the show.
Smith & Wesson Model 686
What appears to be a Smith & Wesson Model 686 .357 Magnum revolver can be seen in the "Negro Y Azul" music video. It is sitting next to several bags of the Walt's signature blue meth.
