Maniac is a 1980 cult horror slasher/splatter directed by William Lustig and co-written by known character actor Joe Spinell. It is mostly notable for Spinell's portrayal of a psychotic serial killer Frank Zito as well as incredible special make-up effects by genre guru Tom Savini and neo-noir dark romantic depiction of New York, all these while not being stripped of social content and sense.
A sequel, Maniac 2: Mr. Robbie was partially filmed in 1986 but abandoned and eventually not completed after Spinnel's death in 1989. Another half-abandoned idea was the crossover with Maniac Cop franchise (though, Maniac Cop 2 still has a similar character portrayed by Leo Rossi, as well as being dedicated to Spinell who is nicknamed "Maniac" in the end credits). Also in 1989, movie was unofficially remade in Greece as The Sigrou Street Strangler. In 2012, an official remake (produced by Lustig) starring Elijah Wood as Frank Zito premiered in Cannes, followed by successful theatrical and video releases in 2013.
The following weapons were used in the film Maniac:
Frank Zito (Joe Spinell) uses a 12 Gauge Double Barreled Shotgun in the most famous scene of the movie, where he shoots disco boy (special effect makeup artist Tom Savini) and disco girl (Hyla Marrow) with it in their car. Zito uses a violin case to illegally hide his weapon, when he's in the city.
Benjamin EB22
Frank Zito uses thr Benjamin EB22 air pistol (an older version with an attached front sight) held in a special case, while practicing shooting in his apartment. He doesn't fire this pistol in the movie, but there are bullet holes in the wall (a little bit bigger then a .22 pellet should do, though), presumably made with the use of this pistol.