Winchester Liberator
Back in the '60s, some guy named Hillberg went to work designing a gun specifically for insurgencies (Back before the AK-47 became the universal weapon of insurgents everywhere). This gun had to be able to be easily used by an untrained person, with reasonable power. Also, it had to be really cheap and simple. In '64, he got a patent for what Quake fans will instantly recognize as a Quad Shotgun. It's essentially a scaled-up version of the Compact Off-Duty Police (COP, the four-barreled gun in Blade Runner) with a foregrip and wire stock. Four-barrel guns like this use a rotating striker that switches barrels after each shot, to provide rapid fire without having to use four triggers.

Hillberg took his design to Winchester, Winchester took it to DARPA, and they called it the Liberator Project, after the shitty WWII zip guns. Winchester estimated that it could build these guns for $20 apice ($20 in '60s money is still pretty cheap). Mark II was chambered in 16ga with a clunky trigger-grip, and Mark III was chambered in 12ga, with an actual trigger, to provide accuracy at range when loading slugs.

This is the fancy new Mk3 version.

Here are the publically availiable documents from the '64 patent (Liberator Mk2).
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