The Fire Sword is a melee weapon, and one of the few items we know the stats of.
The Fire Sword is a 2-Handed Sword, and it is currently the 2nd most powerful known weapon in the game, bested by the Demonic Axe. It is the only item of Epic rarity to be revealed, as of yet. It has a unique ability: Enemies hit have a chance to be set on fire.
When held, small flames can be seen emanating from the blade.