The Voltaic Fist is a boss that is only available in Wargames. Once you reach the Voltaic Fist boss fight you will have to shoot the yellow spot on his back or you might as well unload your guns on the wall.
Killing him will give you epic, and sometimes even legendary loot. Also after a little while, you might get things like the OG Moneymaker or the Skull Blaster 3000, so keep trying because you can get some pretty awesome items.
Some of these items are:
-Midnite's Invictus Boots (Legendary)
-OG Moneymaker Sniper Rifle (Legendary)
-Wintermute SMG (Legendary)
-Midnite's Invictus Shoulders (Legendary)
-Invictus Boots (Legendary)
-Kestrei SJ-87 Pistol (Legendary)
-Muu 89 "Chaser" Machine Gun (Legendary)
-Skull Blaster 3000 Auto Rifle (Epic)
-Nordic Guard '49 Auto Rifle (Epic)
-Peregrine Pistol (Epic)
-Nordic Guard '79 SMG (Epic)
-Nordic Guard '83 Shotgun (Epic)
-Brussell Sniper Rifle (Epic)
There are more items, which will be added soon.