Sterling Archer's primary sidearm is a Walther PPK. In the early episodes, the pistol lacked detail, but by the end of season 2, there was such much detail, the serial number was visible.
M1911
M1911A1 pistols appeared in season 2. It is the sidearm of Ray Gillette. Archer uses it in "Placebo Effect," mainly as a tribute to Magnum P.I. None of the M1911s in the series appear to have safeties, however.
Mauser M712 Schnellfeuer
Manfred has a Mauser M712 Schnellfeuer as his sidearm, using it to shoot Torvald Utne (not the Olympic shot-putter) in "Killing Utne." It is revealed in flashbacks that Malory Archer also used one when she was a field agent ("Double Deuce.)
Beretta 92F
Captain Lammers uses a Beretta 92F in "Skytanic." Archer also uses a suppressed Beretta 92F in one scene in "Skorpio."
Tokarev TT-33
In the "Archer" universe, the official sidearm of Soviet Forces is still the Tokarev TT-33 Pistol.
Webley_Mk_VI
Woodhouse's old World War I squadron mate brings by a Webley Mk VI that had belonged to his old friend, Captain Reggie Thistleton in "Double Deuce." This is one of the few firearms referred to by name on this show. This Webley is later used to knock Archer out.
SIG-Sauer P220 series
Lana Kane carries a pair of SIG-Sauer P220 series pistols in a shoulder rig, but has never actually used them, so it's impossible to determine exactly what type of SIG-Sauer pistol or pistols she has.
Smith & Wesson Model 629
Since retiring from the field, Malory Archer's primary handgun is a Smith & Wesson Model 629, tricked out with a scope and laser. She sleeps with it by her beside in "Dial M for Mother." She mentions that it is a .44 Magnum during a flashback in "Pipeline Fever."
Desert Eagle Mark VII
Archer's rival, Barry Dillon, carries a nickel Desert Eagle Mark VII, which he talks TO, not WITH. Lana Kane also uses a nickel Desert Eagle on occasion.
Luger P08
Krenshaw/Kremensky uses a Luger P08 in the first episode, "Mole Hunt." Lugers later show up in "Double Deuce" and "El Secuestro."
M1917 Revolver
A M1917 Revolver is shown on the a table in "El Secuestro."
Smith & Wesson Model 67
A sky marshal pulls a Smith & Wesson Model 67 when Archer pulls out his sawed-off double barreled shotgun ON A PLANE.
Colt Python
Woodhouse wields a Colt Python in a flashback in "Blood Test."
Shotguns
Sawed-off Double Barreled Shotgun
When he doesn't have to worry about concealment (and even when he does) Archer carries a Sawed-off double barreled shotgun that he "borrowed" from Woodhouse in "Pipeline Fever." Woodhouse is also shown using (presumably) the same gun in flashbacks.
Submachine Guns
TEC-9
Lana Kane is often seen with a pair of TEC-9's, which would be a good fit for her Johnny Bench-ian, steam-shovelly, Truckasaurus hands. According to the dialogue, they are TEC-9s, and fire full auto, but lack the sling rings of a TEC-9. Later in season 2, she can be seen carrying them in her shoulder rig. Archer takes one in "Swiss Miss."
MP40
The MP40 is the SMG seen most on "Archer." ODIN agents use it almost exclusively, as do gay interior decorators/assassins for hire Charles and Rudy in "Honeypot."
PPSh-41
KGB defector Katya Kasanova uses a PPSh-41 to rescue Archer in the Soviet Union in "White Nights."
Steyr TMP
Some members of a Cuban hit squad are armed with Steyr TMP SMGs ("Diversity Hire.")
Uzi
Other members of the Cuban hit squad are armed with Uzi SMGs ("Diversity Hire.")
Rifles
AK-47
The AK-47 shows up numerous times during the series. They appear to be based on real AK-47s, with the milled receiver and open-topped front site.
M14
Cyril channels Private Pyle from Full Metal Jacket with an M14 after Lana decides to sleep with all the men at ISIS as a form of revenge in "Dial M for Mother."
M21
An M21 rifle is seen in a crate during a flashback to the last moments of Agents Ruiz, Pak, and Bgumbe (all of which recycle the same background) in "Diversity Hire."
Heckler & Koch MSG90
Except in one instance, the H&K MSG90 is the primary sniper rifle of ISIS.
Walther WA 2000
Archer uses a Walther WA 2000 sniper rifle in "Placebo Effect" to take out some guards.
Mauser Gewehr 1898
A German sniper sees Woodhouse and Reggie after Woodhouse braves No Man's Land to save Reggie in "Double Deuce." The bolt is on the wrong side of the rifle.