I once ran a campaign based on Fred Saberhagen's books of swords. I'm the books there are twelve swords that would be considered greater artifacts. One of my players was playing a pacifist. He picked up the sword called Townsaver while his village was being invaded. Anyone who has read the books knows this same situation happens right at the beginning of the series. The sword takes over, because it's power is to force anyone who holds it to protect unarmed innocents. He proceeded to slaughter the invading force. He was devastated.
It's worth reading the whole series of you're interested. They aren't awesome, but they are fairly quick reads, and the way he resolves the story is interesting.