This brings to my mind Saberhagen's Swords (or Lost Swords) books, a series about 12 swords, each an artifact with a supreme power. One brings the owner impossibly good luck, another reflects one's enemies attacks perfectly back to the originator, another is guaranteed to slay any dragon, etc.
Of the 12, one of the ones that was most feared was Woundhealer. Anyone "cut" or "stabbed" by Woundhealer was healed, even regrowing amputated limbs (although something that extensive could take several months). The reason it was feared was because the owner would thrust it through his heart, then lay hands on conventional weapons and stride off to battle. Completely invincible, so long as no one pulled Woundhealer from his heart...