Them!

The weapons seen in this 1954 movie are:

M20 "Super Bazooka" (3.5" Rocket)

Used Sgt. Ben Peterson (James Whitmore) and Major Kibbee (Sean McClory).

M20 "Super Bazooka" 3.5"

Peterson, enjoying himself a little too much, takes aim.

Another bazooka used by Kibbee.

M1 Flamethrower

Peterson wears an M1 Flamethrower accompanying Pat and Graham into the nest.

Schematical drawing of M1A1 Flamethrower

Peterson (right) wearing the flamethrower as the group enters the nest.

Peterson roasts a giant ant that comes out of the wall.

Peterson prepares to torch the queen's chamber.

After his service revolver fails to slay the giant ant, Peterson runs and gets this from his patrol car. Needless to say it packs a bit more of a punch. Agent Graham and several soldiers use them in later scenes as well.

M1928A1 Thompson with 30-round magazine and early 'simplified' rear sight that would be adopted for the M1 Thompson - .45 ACP

Peterson locks and loads.

Peterson gets medieval on the ant's abdomen.

Graham firing an M1928 Thompson with his eyes shut at the film's climax.

Colt Official Police

Doomed redshirt Trooper Ed Blackburn (Chris Drake) uses a Colt Official Police revolver. Later, Trooper Sgt. Ben Peterson (James Whitmore) uses a Colt Official Police to shoot at a giant ant.

Blackburn unholsters his weapon and turns the light out so the unknown assailant (unknown to him, a giant ant) won't see him emerging from the room.

Blackburn prepares to meet his maker courtesy of giant mandibles.

Peterson shoots at the ant.

Peterson comes to the conclusion his service revolver isn't doing much good.

Colt Detective Special

A Colt Detective Special is found by Sgt. Peterson in the destroyed camper at the beginning of the movie. FBI Agent Robert Graham (James Arness) shoots at an ant with a Colt Detective Special of his own later.