Lightning gun

The lightning gun is a new energy weapon which appears in the multiplayer and SnapMap modes of the Doom game. It fires a constant beam of directed electricity (presumably via technology). It can attack either directly, or via splash damage-inducing electrical discharges targeted at the floor.

"Short range energy weapon that fires a constant stream of electricity."

- SnapMap description

Pre-release
In The Art of DOOM, the concept for the lightning gun is called the ARC cannon. It is stated to have been conceived by the UAC as a counterpart to the plasma rifle designed at the Advanced Research Complex and based on research into Argent conductivity. It utilizes modulation of the plasma current to achieve a sustained linear stream of discharge which is destructive to biological forms. Its production was stated to be limited, perhaps meant as a nod to its eventual multiplayer-only status.