Firelance

Firelance is a lightweight, yet powerful, weapon that uses the same ammo type as the Alien Blaster. It also sets the target on fire, like the Flamethrower or Shishkebab, causing 2 points of damage every 5 seconds.

Appearances
The Firelance appears only in Fallout 3. It is primarily obtained from a random event, though it can sometimes be found on random NPCs in the Capital Wasteland.

The random event has a better chance of happening with a higher luck skill. There will be a sound like a jet flying overhead, followed by an explosion. Then something crashing and skittering across the ground will be heard, similar to knocking over a large object. At night, the explosion looks similar a plasma rifle shot impacting; during the day, it looks like a frag mine going off.

After the explosion, the immediate area will be strewn with Alien Power Cell ammo and the Firelance. Unfortunately, it is in no particular pattern, and the player will have to search the immediate area to find the ammo (there are 24 total) and the Firelance on their own.

In Wasteland, which served as inspiration for the Fallout games, the Firelance is a weapon mentioned in the Paragraph Book included with the game.

HINT: Dogmeat is incredibly useful for this situation, as he can be told to search for a weapon and he'll fetch the Firelance. Dogmeat can also search for ammo and retrieve the alien power cells. Alternatively, wait until nighttime and look for the ammo, which glows blue in the dark. Also you will sometimes encounter Enclave Troopers wielding the firelance. I also found a raider weilding it and as I was a lower level at the time, he almost killed me. Not sure whether this was a random encounter or just a normal raider picking it up, it was near the mereseti trainyard though.