Minigun

A minigun is a multi-barrel machine gun with a high rate of fire, employing gatling-style rotating barrels. It was a standard military weapon before the Great War, with Rockwell's CZ series being the most popular choice in the United States of America.

It is widely used by many factions such as the super mutants, Brotherhood of Steel and the Enclave, due to its extraordinary firepower at close range.

CZ53 personal minigun
 A Rockwell CZ53 personal minigun firing 5mm ammunition at over 60,000 RPM with an ammo capacity of 120x 5mm round. The CZ53 personal minigun makes up for the small 5mm round by sending a hail of bullets toward its target. Its sheer size, coupled with its trademark sound, is enough to send anyone in its path running for cover. It's a great weapon for suppressing fire, letting others flank the unsuspecting enemy. When the Great War struck, it was already an aging design and was slowly being replaced by the more advanced CZ57 Avenger minigun. It's the favorite weapon of the Mariposa super mutants during the Unity's time. 

CZ53 personal minigun backpack
A variant model of the regular CZ53 personal minigun with six barrels linked into pairs, four barrels in the top and two in the bottom, a cage underneath to put the ammo box containing 240x 5mm round, and used in combination with a backpack.
 * For the unique version found in Fallout 3, see: Eugene

5mm CZ57 Avenger minigun
 Rockwell designed the 5mm CZ57 Avenger as the replacement for their aging CZ53 personal minigun. The Avenger's design improvements include improved gel-fin cooling and chromium plated barrel-bores, giving it a greater range and lethality. It also keep an ammo capacity of 120x 5mm round.

5mm CZ57 Avenger minigun backpack
A rare variant model of the regular 5mm CZ57 Avenger minigun with rusty metallic plate, a cage underneath to put the ammo box containing 120x 5mm round, and used in combination with a backpack.

5.56mm CZ57 Avenger minigun
A variant model of the regular CZ57 Avenger minigun seen in the Midwest which is more compact, completely black, less powerful and chambered for 5.56mm bullets with an ammo capacity of 120x 5.56mm round.

4.7mm Vindicator minigun
A Rheinmetall AG 4.7mm Vindicator minigun firing 4.7mm ammunition at over 90,000 caseless shells per minute down its six carbon-polymer barrels, and with an ammo capacity of 100x 4.7mm round.

7.62mm Vindicator minigun
A variant model of the regular Vindicator minigun seen in the Midwest with a completely new design, a display screen that show the remaining ammunition and chambered in 7.62mm bullets with an ammo capacity of 100x 7.62mm round.

MEC Gauss minigun
An extremely rare minigun, the MEC Gauss minigun was designed by the Chinese. Atypical for an automatic weapon, it uses Gauss technology, multiple electromagnetic fields to firing 2mm ammunition at over 90,000 rounds per minute to relativistic velocities, with an ammo capacity of 80x 2mm round.

Vault-Tec 9mm minigun
 A post-War minigun designed by Vault-Tec in the Secret Vault. The Vault-Tec 9mm minigun has a lower rate of fire than a general minigun but chambered in 9mm, an uncommon high caliber for a minigun. It has five barrels and it used by the Attis army in Texas. 

CZ25 military minigun
A Rockwell CZ25 military minigun firing .223 ammunition with an ammo capacity of 54x .223 round.

Behind the scenes

 * The Avenger might be named after the GAU-8 Avenger 30mm Gatling-type rotary cannon mounted on the A-10 Thunderbolt II.
 * The CZ designation could possibly be a reference to the real-world weapon manufacturer, Česká zbrojovka (famous for CZ-75 pistol or Skorpion submachine gun).