An Astra 400 was used in Season 3's "Dead Man Sliding" (S3E10) as a futuristic looking tranquilizer gun by Contestant Coordinator Taryn Miller (Perrey Reeves). A laser was clamped onto the locked-back slide to make it appear futuristic.
The Glock 17 was first used in the Pilot episode when Quinn Mallory (Jerry O'Connell) was given one of these pistols by a resistance fighter on the world where America was occupied by the Soviet Union. These pistols subsequently appeared in quite a few other episodes.
The Beretta 92FS was another pistol which appeared quite regularly on the show. Maggie Beckett (Kari Wuhrer) carried one in several episodes, on at least one occasion with a suppressor.
The USSR soldiers in "Pilot" (S1E01) were armed mostly with Norinco Type 56 copies of the AK-47 assault rifle. These rifles were also seen in many other episodes. In "Slither" (S3E22), both Quinn Mallory and Rembrandt Brown (Cleavant Derricks) used Type 56 rifles after taking them from tobacco farmers (on a world where tobacco was illegal).
The USSR soldiers in "Pilot" (S1E01) were also armed with many Norinco Type 84S assault rifles, including at least one Type 84S Target with a long RPK-style barrel.
Error creating thumbnail: File missingNorinco Type 84 5.56x45mmError creating thumbnail: File missingNorinco Type 84S "Target" Rifle - 5.56x45mm. Basically a standard Norinco Type 84S with a slightly longer barrel. This variant was ready for export after the 1989 US import ban, so it is mostly seen in Canada. It has an 18.5" barrel and was not really seen in the U.S. Gun market.Error creating thumbnail: File missingOn the left, a soldier with the Type 84 rifle in "Pilot" (S1E01).
M16A1
In the Pilot, anti-Soviet resistance fighters were armed mostly with M16A1 assault rifles. Hilariously, the resistance fighters' T-shirts showed the Statue of Liberty holding an M16A1 above her head (in defiance of similar Marxist-Leninist-themed T-shirts and flags).
M16A1s were also used in many episodes by military personnel, usually with M16A2-style hand guards, including Colonel Rickman's (Roger Daltrey's) Marines, and also Maggie Beckett (Kari Wuhrer) in "Dinoslide" (S2E23).
Beginning in Season 3, when the production of the show moved to Los Angeles, M16A2 assault rifles were commonly seen, notably by Colonel Rickman's (Roger Daltrey's) Marines in the episodes "The Exodus, Part 1" (S3E16) and "The Exodus, Part 2" (S3E17). Most of the M16A2s in the show do not appear to have been genuine M16A2s: The glossy black finish on most of the rifles suggests that they are actually Olympic Arms K4B copies.
Quinn Mallory was seen using what appears to be another M16A2 in the episode "Dinoslide" (S3E23), which was also later used by Wade (Sabrina Lloyd) to shoot at the T.rex. Upon closer inspection: The rifle used by Quinn and Wade has a "slab side" lower receiver and no bayonet lug; these characteristics indicate that the weapon is actually an early Colt AR-15A2 Sporter HBAR that has been converted to full-auto. In the 1980s and 1990s, Colt's heavy-barreled AR-15s typically lacked the bayonet lugs, since this feature was not necessary for target rifles, as compared to military rifles.
Error creating thumbnail: File missingQuinn and Maggie hunt for Col Rickman in "Dinoslide" (S3E23). Note that Quinn's rifle has a "slab side" lower receiver and indented forward pushpin, indicating that it is a civilian AR-15 A2 variant and not a mil-spec M16A2.Error creating thumbnail: File missingQuinn and Maggie take cover in a cave from the T.rex in "Dinoslide" (S3E23). Quinn's rifle lacks a bayonet lug on the front sight tower in this image, again indicating that it is an AR-15 A2 Sporter HBAR and not an actual M16A2.Error creating thumbnail: File missingWade holds the AR-15 A2 Sporter HBAR in "Dinoslide" (S3E23). Again, note lack of bayonet lug.
Submachine Guns
Heckler & Koch MP5A3
The Heckler & Koch MP5A3 submachine gun first appeared in "Fever" (S1E03), seen used by the California Health Department soldiers.
In "Pilot" (S1E01), a resistance fighter is seen using a Cetme Ameli light machine gun mounted to a Steadicam harness (similar to the M56 Smart Gun from the film Aliens).