Flamethrower

From Doom Wiki

The flamethrower is a weapon from Strife, used both by the player, and by the Crusader enemy. It shoots balls of fire. The flamethrower can only be used over a short range as the fireballs are subject to gravity. Most human and humanoid enemies will set ablaze, doing fire damage to nearby human actors when hit with a fatal blow of the flamethrower. Another tip is that the Environmental Suit can also block the flames completely, making it very useful in close-range combat with Crusaders.

A complete flamethrower can be acquired by getting the flamethrower parts from Weran and then taking them to Irale. You can also pick one up in a hidden area of Fortress: Security Complex.

This weapon consumes Energy cells which are shared with the Mauler.