There was an indie game that was released a few years ago. Don't think it ever made it to Steam or anything. It was, in fact, free. Might still be for all I know.
Anyway, the big pull for the game was the morality of it. It was a side-scrolling action game similar in someways to Flashback or Out of this World. Except, if you didn't kill any of the enemies, but rather avoided them, they would start to hesitate...and then not attack at all unless you provoked them. It became part of the story, too.
But yeah, I can't for the life of me remember the name of it. Does this ring a bell for anyone?