The Flamethrower is a scrapped weapon in Duke Nukem 3D.
The Flamethrower would… basically just shoot flames at enemies.
Working code for the Flamethrower can be found in the v0.99 prototype and can be accessed via hacking. The v0.99 version shows that the Flamethrower causes enemies to switch to a darker palette and become slightly larger when hit by its projectiles. When killed, they would die as normal, but a flame effect appears over their dead body. The message “COOK ‘EM GOOD!” is then displayed on the top of the screen when the player starts to fire the Flamethrower, but would disappear after the player stopped firing it for a second or two.
The Flamethrower was scrapped. Judging by its look in the previously-mentioned pre-release screenshot, it was very likely that the Flamethrower was replaced by the Freezethrower. This change appears to have done at the last minute, as the Flamethrower appears in working (but glitchy) condition in the v0.99 prototype (January 7th, 1996), but was completely replaced by the Freezethrower (January 21st, 1996).
The Enforcer was also supposed to wield the flamethrower at one time. Pictures of it using the Flamethrower can be seen in pre-release screenshots. In Nuclear Showdown V1, The Enforcer wield the flamethrower.