So I was playing through Dishonored recently (which is generally a great game and tickled all of my stealthrogenous zones), and went for the non-lethal, minimal-contact approach. I noticed that in the loading screens the game effectively said, "If you choose not to kill many people you will get a pat on the head and cookie at the end of the game and everything will be sunshine and rainbows." I've also heard from friends who went for high-chaos runs that if you actually use the many, many, many, many different ways of killing people (as opposed to the two ways you can take people out non-lethally) then at the end of a game a character calls you a sick monster and you get a doom-and-gloom ending.
Personally, I think that moral choice systems in games get a bit lame when A) they are simple and binary with no grey areas and B) you get awarded "good karma" and "bad karma" points as an incentive for certain actions.
I tend to almost always take the good karma path anyway because I find it easier to get invested in the game when I'm not playing the role of an evil jerk, but I hear a lot of people have fun playing as the villain. In games like Infamous, Mass Effect, and Dishonored, which path do you prefer to take?