The M1911A1 is seen used by several members of Bravo Company, including Lt. Myron Goldman (Stephen Caffrey).
Smith & Wesson Model 10 Revolver
In "Roadrunner" (S1E10), USAF CPT J.T Slaney (William Allen Young) carries a Smith & Wesson Model 10 revolver as his sidearm. This also appears to be the revolver used by a VC Peasant Woman (Tamlyn Tomita) in "Sitting Ducks" (S1E04). IT also appears to be used by the injured Vietnam Vet after he takes it from the security guard in "Soldiers" (S1E14)
Tokarev TT-33
NVA officers and some other characters can be seen armed with the Tokarev TT-33 pistols.
Rifles
M16 Variants
The M16 rifle was the main rifle of the U.S. Army soldiers in Vietnam and is seen carried by most of the platoon. In the series, various models of the M16 are seen.
Colt XM177 (Colt Sporter Carbine)
A Colt Sporter Carbine modified to resemble the XM177 rifle is mainly seen being used by SFC Clayton "Zeke" Anderson (Terence Knox). In Season 1's "Under Siege", Anderson's Colt Carbine is seen loaded with a 30-round magazine (unusual for the time period of the series). For the remainder of the series, the Colt is loaded with the more accurate 20 round magazine.
M1 Garand
In "Dislocations" (S1E02), a villager named Dep (April Tran) is armed with an M1 Garand.
Norinco Type 56
The Norinco Type 56 is seen in the hands of the NVA and VC soldiers.
The SKS rifle is seen a couple of times used by VC soldiers.
Full-length Mosin Nagant Rifle
Shotguns
Ithaca 37 "Stakeout"
The Ithaca 37 "Stakeout"-style shotgun is seen in the hands of SFC Clayton "Zeke" Anderson (Terence Knox) in Season 1.
Machine Guns
M60
The M60 is mainly seen carried by Pvt. Alberto Ruiz (Ramon Franco) in the series.
M60D
The "D" variant of the M60 is seen mounted on Huey helicopters as well as fired by enemy forces in the series.
Browning M2 HB
A Browning M2 .50 cal is seen mounted on US vehicles throughout the series.
Soviet SGM Goryunov (mocked up from Browning M1919)
What appears to be a Soviet Goryunov SGM Machine Gun or Chinese Type 57 machine gun is also seen used by NVA forces in the series. In reality, this machine gun was a visually modified Browning M1919.
Valmet M78
NVA forces are sometimes seen firing the Valmet M78 (which was used as a substitute for the more accurate RPK machine gun).
Hand Grenades
Mk 2 Hand Grenade
In "Pilot" (S1E00), SFC Anderson as well as other soldiers are seen carrying Mk 2 hand grenades. This grenades were more commonly seen during WWII and the Korean War, but were still being used in Vietnam.
M26 Hand Grenade
The M26 hand grenade is the more common grenade carried by US troops in the series.
M6A1 Gas Grenade
In "Notes from the Underground" (S1E01), Lt. Goldman is seen tossing an M6A1 Gas Grenade into a VC tunnel.
M18 Smoke Grenade
M18 smoke grenades are also carried by the men of Bravo Company in the series.
The Chinese Type 67 stick grenade is seen also used by enemy forces in the series. In "Pilot" (S1E00), a variety of enemy weapons is seen on a table, one of which appears to be a Type 67.
Grenade Launchers
M79 Grenade Launcher
The M79 grenade launcher is seen used by US forces throughout the series including SFC Anderson and Johnson.
M72 LAW
The M72 LAW is seen used by US troops throughout the series.
RPG-7
The RPG-7 is used throughout the series by VC and NVA forces.
Other
M2 Flamethrower
An M2 Flamethrower is prominently seen in "Pushin' Too Hard" (S1E11). Anderson is seen using it on a machine gun bunker in the episode.
M18A1 Claymore
M224 Mortar
M29 Mortar
The M29 Mortar is seen used in the firebase, notably in "Under Siege" (S1E13).
M102 Howitzer
The M102 Howitzer is seen used in the firebase in "Under Siege" (S1E13).
F-4 Phantom II
A pair of F-4 Phantom II jets are seen making a napalm run in "The Battling Baker Brothers". These are authentic planes, as the production received some support from the US Department of Defense in Season 1.