Jin's Helm of the Dervish (3.5e Equipment)
From D&D Wiki
Jin's Helm of the Dervish: This simple skull cap style helmet has a four foot long braided horse hair top-knot with a simple dagger blade woven into the end. Simple cheek guards extend down from the skull cap to protect the wearer's face. In the hands of a non-dervish, this helmet simply confers darkvision as the spell. In the hands, or more appropriately, on the head of a dervish, this helmet also confers weapon proficiency with the dagger whip and allows the user to make one additional attack with the whip dagger as part of their dervish dance special ability. The dagger does a single point of damage, is masterwork, and can be enchanted as normal. Typical specimens are +1 daggers.
The cost of the magic dagger is calculated separately and added to the cost of the Helm (i.e. the cost of a +1 Dagger would be 2,000 gp added to the 20,000 gp for the helm for a total price of 22,000 gp).