Super shotgun

The super shotgun, also called "combat shotgun" in the manuals or otherwise "double-barreled shotgun" or often abbreviated to "SSG" is a sawed-off, break-action, double-barreled shotgun in contrast to the original shotgun which is pump-action and single-barreled.

Background
The Combat Shotgun is a new acquistion by the Marine Corps inventory and soem of the troops have taken to calling it the "supershotgun." It uses the same ammo as the Pump Shotgun, but at twice the rate. It also kicks twice as bad, which doubles your recovery time between shots. On the upside, however, it offers three times the stopping power. If you want to let the air out of floating gasbags like Cacodemons and Pain Elementals, stick one of these in their eye sockets and pull the triger. Sayonara slimeball!

Other id Software games
After its introduction in Doom 2, the side by side double-barreled shotgun became a mainstay in both the Doom and Quake series. It serves as a slow reloading, but powerful close-range weapon.

Doom 64
In Doom 64, the super shotgun fires much quicker, nearly as fast as the regular shotgun. It does not have the reloading animation that is present in the PC versions of Doom either, which is also the case with the normal shotgun's cocking animation. In addition, the gun knocks the player back a bit when fired.

Quake series
In Quake the Double-Barrelled Shotgun is the main close-range weapon. The rate of fire is noticeably higher in comparison to the Doom 2 Super shotgun. Quake II has the Super Shotgun with a rather unusual pump-action mechanism. In Quake III Arena, the double-barreled Shotgun is the only shotgun in the arsenal.