The flamethrower was a weapon that was, at some point, going to appear in ObsCure II. While it didn't make it to that game, it was later added to Final Exam.
ObsCure II[]
The flamethrower was planned to be part of the game, but seemingly never got added into the game, tho it's likely that the development team couldn't get it working properly in time for release, or it was perhaps too overpowered. It's likely that the team never even got to start working on it, as all we really have of it is a pre-rendered model by one of the game's artists[1].
It appears that the weapon is crafted with a water gun (presumably loaded with gasoline) with a wick placed in front of the barrel. Obviously the ignition of the wick would have ignited the flammable liquid fired to obtain a jet of flame.
Presumably it would've been remarkably effective weapon against enemies, and likely a secret weapon obtained in the weapon boxes.
Final Exam[]
The flamethrower can be obtained in the locker room of the gym in Leafmore High in the chapter "Imminent Care". It shoots waves of fire that burn enemies, slowly damaging them, the fire ensures continued damage. The weapon holds 10 ammo points, with a maximum of 20 in reserve. Despite being extraordinarily effective weapon, the charging time is extremely long, making it necessary to reload only when far from enemies to avoid unwanted damage.