A video showing the Flamethrower weapon type and some of its abilities.
Flamethrowers are used generally for dealing with Symbiote Monsters, many of which have a whopping 10x weakness to Fire.
Competencies shown in the video include:
Flamethrower Area - Boosts the area of effect of Flamethrower attacks. Flamethrower Range - Boosts the range of Flamethrower attacks. Detonate - Flamethrower attack that uses all remaining ammo to deal Fire damage to an area around the user. Immolation Boost - Boosts damage dealt when Symbiote Clouds are immolated. Generally difficult to do with a Flamethrower due to its short range (and best used with exploding Barrels), but Flamethrower skill trees tend to contain these. Dark Energy - All Fire attacks take an enemy's positive Elemental Defense and turn it negative for the attack, making Flamethrowers effective against enemies normally resistant to Fire.