Them!

The weapons seen in this 1954 movie are:

M20 "Super Bazooka" (3.5" Rocket)

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

M20 "Super Bazooka" 3.5"

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

Another bazooka used by Kibbee.

M1 Flamethrower

Used by U.S Army Soldiers.

Schematical drawing of M1A1 Flamethrower

M1928 Thompson

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. This may be a Thompson.

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.

Blackburn's revolver

Doomed redshirt Trooper Ed Blackburn (Chris Drake) uses this revolver.

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's revolver

Trooper Sgt. Ben Peterson (James Whitmore) uses this holstered revolver to shoot at a giant ant.

Peterson shoots at the ant.

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

Graham's revolver

FBI Agent Robert Graham (James Arness) shoots at an ant with a small snub-nosed (?) revolver.

Graham is told by an offscreen Dr. Medford to go for the antennae.

He does precisely that.

Snub-nosed revolver

A snub-nosed revolver is found by Sgt. Peterson in the destroyed camper at the beginning of the movie.

The revolver lying on the floor.

Sliding a pencil into the barrel, Peterson picks the revolver up to examine it.

Lever-action rifle

A lever-action rifle, described as a 30-30, is found at Gramps Johnson's store with the barrel bent in half.

The rifle lying on the floor.

Peterson examines the weapon as Blackburn looks on.

Captain Edwards examines the gun.