Mrs. Peenman (Nancy Fish) uses a Mossberg 500 shotgun to shoot at Stanley Ipkiss (Jim Carrey) when he first puts on the Mask and reaks havoc in her apartment. Lt. Mitch Kellaway (Peter Riegert) tells Ipkiss that she fired a couple of rounds of "20-ought-buck", which makes no sense whatsoever to us who actually know something about guns.
M1928 Thompson
When a group of street thugs attempt to rob Stanley Ipkiss (Jim Carrey) while he is wearing the Mask, he makes several balloon animals to humor their stupidity before building his "personal favorite", an M1928 Thompson.
Glock 19
Freeze (Reginald E. Cathey) is seen armed with a Glock 19 during the failed bank robbery. Several of Niko's (Orestes Matacena) thugs during the shootout in the Coca Bongo club are also seen with G19s, one of which has a chrome slide.
Dorian Tyrell's (Peter Greene) sidearm in the film is a Star Firestar M-43 9mm with a nickel finish, which he uses to shoot at Ipkiss/Mask (Jim Carrey) in the Coco Bongo club.
Niko (Orestes Matacena) draws a chrome Jericho 941 to defend himself during the shootout in the Coco Bongo club. Since Dorian (Peter Greene) is wearing the Mask, he allows Niko to shoot him several times, which has no effect on him. He then sucks up the bullets and fires them out of his mouth, killing Niko.
Dorian's Mouth
Using the power of the Mask, Dorian Tyrell (Peter Greene) allows Niko (Orestes Matacena) to shoot him several times (which he shrugs off) and then sucks up the bullets and fires them from his mouth. Since his mouth isn't actually a firearm, this was added to mainly reveal some goofs present (even though firing bullets from your mouth could be considered a goof...).