The Blade of Sank'ou'net (3.5e Equipment)
From D&D Wiki
This is a scimitar of of the great Sank'ou'net an emperor who was well known for his crafting of blades. This blade is vibrating slightly giving it the ability to easily slice through enemies by vibrating the cells of the skin out of the way. The story goes that when Sank'ou'net made the blade he passed it down to his only son and ordered his son to kill him with it.
The Blade of Sank'ou'net can be used with Weapon Finesse, even though it is not a light weapon.