An M60 machine gun is used by John Rambo (Sylvester Stallone) near the end of the film when he removes it from the back of a personel truck and uses it to shoot up the police station.
AR-15/SP1
The police officers use AR-15/SP1 rifles as noted by their slab-side recievers lacking a forward assist. When fired in the film the guns are semi-automatic, further hinting they are civilian guns. When the guns fire fully automatic, they switch to M16A1s.
M16A1
M16A1 rifles are used by several members of the police while they hunt down John Rambo. These guns replace the AR-15/SP1 when the officers fire fully-automatic. Members of the National Guard use them as well.
Heckler & Koch HK93
A Heckler & Koch HK93 is used by Sheriff Will Teasle (Brian Dennehy) while hunting Rambo. It is noted by its curved box magazine and full stock.
M72 LAW
The M72 LAW (Light Anti-tank Weapon) is a 3 foot disposable single shot launcher capable of penetrating mutiple layers of armor. A member of the national guard fires one into the cave Rambo is hiding in, failing to kill him but trapping him inside.
Winchester Model 88
While in a police chopper, Deputy Sgt. Arthur Galt (Jack Starrett) fires his Winchester Model 88 lever-action rifle at Rambo from a helicopter before falling to his death. Rambo kills two dobermans with the rifle and wounds their owner before it runs out of bullets.
Rambo's Survival Knife
Not a gun but still the star of the Rambo films, Rambo's knife is a survival knife with a screw open hilt butt filled with a suture needle and thread, a compass, and has gnarled teeth to cut barbed wire. It is so sharp it can cut paper like butter. The knife for this movie, and it's sequel Rambo: First Blood Part II were designed by famed knife maker Jimmy Lile.
An officer can be seen briefly firing what looks like a Smith & Wesson Model 10 with a tapered barrel at Rambo when he drives the stolen personel truck.
In an alternate ending, Rambo has Col. Trautman (Richard Crenna) kill him with his M1911A1 sidearm. Trautman aims the gun away but Rambo jams it to the gut and the gun kills him.