The flamethrower was intended to be a area of effect weapon capable of killing a group of aliens and hitting entrenched aliens. It would have been a powerful weapon but very dangerous to the user. If the person using it died it could detonate its fuel tank and injure an ally.
The weapon was cut due to engine constraints.
As the name implies, the flamethrower sprays a jet of incendiary liquid at its target, causing immense damage to anything caught in the blast. The flamethrower completely ignores cover when calculating damage to its victims and is capable of hitting multiple units with a single shot. This makes it invaluable when clearing fortified positions or ambushing enemy units, where a single flamethrower can turn the tide of the battle in seconds.
Unfortunately, the flamethrower also has some major drawbacks, not least being the fact that the user has to carry pressurised containers of highly-flammable liquid around with them. Flamethrowers also damage indiscriminately, destroying items that could otherwise be recovered. It is also highly dangerous if used carelessly, as the user can easily accidentally douse a comrade (or themselves) in napalm when firing the weapon in an enclosed space.