It's a shoulder-mounted recoilless energy weapon, very similar to the tesla cannon, that fires powerful blasts of electricity. With the skill energy charge, you can charge it for equivalent of three merged blasts for three times more damage and ammo, and the impact zone is much greater.
The most powerful energy weapon of the game and one of the best weapons available. Once hit by the explosion, people affected will be electrocuted for about five seconds.
Beware, if you equip it, you can not dodge and each shot consumes 5 heavy energy cell.