Firefly's Flamethrower is a plasma flamethrower which is the only thing hot enough to burn through the ice walls around Mister Freeze's Fortress.
History[]
The flamethrower originally belonged to Firefly but after Gotham fell into disarray following the Joker's takeover and the fall of his tower at the end of "Devil's Snare", Doctor Trap raided all the villain's lairs and put the loot up on display at the Gotham Natural History Museum surrounded by deadly traps.
In "Catwoman, after failing to break into Mister Freeze's lair, his guards accidentally let slip to Harley Quinn and her crew that they needed Firefly's flamethrower to melt through the ice as well as revealing to them where to find it.
On display at the museum
With the help of Poison Ivy and Catwoman, Harley decided to break into the museum to steal it. They work their way through the traps and eventually close in on the flamethrower which is placed in glass display. Catwoman cuts a hole in the the casing but as soon as Harley grabs the flamethrower, a trap triggers and encases them all in a glass prison. As the glass encasing begins to collapse on them, Harley then uses the flamethrower to burn out of the glass casing to escape the trap and goes on to beat up Doctor Trap.
In "Thawing Hearts" Harley finally uses the flamethrower to melt a tunnel through the ice walls around Mister Freeze's Fortress, finally granting her access and then unceremoniously throws it aside.
In "There's No Ivy in Team" Firefly could be seen having gotten his flamethrower back as he used it to burn down the Old Gotham Corn Factory.