Steam Sword (3.5e Equipment)
From D&D Wiki
Crafted by dwarven smiths in the desert city of Titillation, this sword resembles a single-edged masterwork bastard sword with a gear in the pommel and a small pipe lined along the flat side of the blade. Despite its inspired design, this weapon has its drawbacks. The steam sword is a mechanical weapon and requires 2 potion bottles worth of water. It utilizes the natural desert heat to make the water boil and trap steam in its hilt for a devastating heat attack in combat. The sword must have spent a minimum of two hours in the desert sun for the heat engine to work. The wielder of a steam sword must spend a free or swift action to activate the steam sword. When activated, a jet of superheated steam shoots from the pipe along the flat end of the blade. This steam deals 1d4 fire damage, using up the steam in the sword for the day, until such actions are taken to prepare another steam jet. After expelling the steam, the weapon demonstrates its biggest drawback: the steam sword begins to heat up, as if it had been the subject of a heat weapon spell, the reason being the mechanisms inside the sword were imperfectly made, causing the released heat to escape inside the sword.
This sword comes with specially treated gloves that are immune to fire damage, to make sure nobody burns their hands. These gloves have fire resistance/4, making it immune to the steam damage, however, it is still flammable to any amount of fire damage higher than 4, causing the gloves to act as if normal gloves were worn.