A sword that stores the identity of the wielder. To transfuse the soul to the blade, one must first stab himself through the heart. The person will not die, but lose the freedom of the soul upon real death.
Somehow, someway, a band of gnomes learns how to be ninjas. In fine gnomish style, they open an academy to teach this art to other gnomes. Wacky Hijinks ensue. Or the gnomes become some of the finest assassins in the land. Or both.