Tenraibachi (3.5e Equipment)
From D&D Wiki
A blade forged of heaven, it's soul existance is to bring divine punishment to sinners. They allow only those purest of soul to wield it's blade, punishing one else and by cutting their hand, dealing 1 damage. In the hands of a Tenraimusha, it is the worst nightmare of all sinners. It's blade will cut down sinners, inflicting no injury on any one who touches it blade unless they bare a sin that is to be punished. The wielder gets a +10 divine asistance bonus to all attack rolls made against those marked for punishment, but recieves 1 damage and a -20 divine punishment penalty when striking an innocent.
As a katana, the Tenraibachi is wielded as a masterwork bastard sword, wielded in two hands except unless it's wielder takes an exotic weapon proficiency and gives a +1 masterwork bonus to all attack rolls made with it.