"When bullets, shells, and explosives won't get the job done, burn it down!... Satan's own scalding hot shit-stick. Caliente!"
— Description in GTA CW.
It is a mechanical device designed to project a long controllable stream of fire. It is classified as a Heavy Weapon in the later editions. In all of its appearances, the Flamethrower can be easily identified by its large fuel tank, a large barrel and a small rod which contains the small flame.
The Flamethrower in Grand Theft Auto 1 appears to have a traditional appearance, having a shotgun-like design with the flame and the fuel tank on it. In the Grand Theft Auto London expansions, the weapon is much more traditional, with a single barrel that contains the fuel tank on the back and feeds the weapon via a hose that ends next to the flame.
In Grand Theft Auto 2, the Flamethrower assumes a retro-futuristic appearance, having a much lower profile than in its previous appearances. With the fuel tank mounted horizontally and next to the weapon's barrel, the weapon again takes a shotgun-like appearance. There is also a vehicle version of this weapon, the Vehicle Flamethrower.
The renditions after GTA III are not based on any known flamethrower design, so it is assumed that they are homemade Flamethrowers, based on their fuel tanks and triggers. However, its heatshield and part of the barrel appears to have been based on the barrels and heatshields from M2 Browning machine guns.
The Flamethrower in Grand Theft Auto: Chinatown Wars regains its shotgun-like appearance as in the 2D Universe. Based on the Hud icons, the fuel tank is now mounted on a side.
The flames from the flamethrower will only damage vehicles and pedestrians. In GTA San Andreas only, the flames can be created on the ground and can spread, making the fire extremely hard to put out if one is started with the flamethrower, even if only one little flame was made to start out with. The flames on the ground will not affect pedestrians but can affect vehicles and the player. If a pedestrian catches on fire, the pedestrian will usually run wildly until his or her death.
If you activate the flamethrower in front of a mirror, the fire will not show up on it.
Harwood, Portland Island - On roof of the Head Radio building. It will be on a block-like object. This object is too high for the character to jump on, so you must plan accordingly in order to get there. A Hidden Package will be nearby. There is a video here
Hideouts - Available after extinguishing total 20 fires on each island in the Firefightervehicle mission. It should be noted the Flamethrower can be obtained very early in the game, provided the player get to Staunton Island by jumping the girder and steel beam on the broken Callahan Bridge (both left and right side). Since Shoreside Vale is not locked at this point the in game, the player can easily drive to it using either the Subway or the Porter Tunnel. He can then complete the 20 firefighting missions there, come back, do the same at Staunton before going back to Portland. This will make the Flame Thrower appear even if the player haven't completed any missions in Portland.
Viceport, Vice City Mainland - By the building near the road in the southwest part of Viceport, south of the Viceport Pay 'n' Spray. From the Viceport Pay 'n' Spray, head south along the road. As you near the road curve going east, you should see the weapon icon to your right.