You know how you could potentially (not realistically) go through Metal Gear series games without killing a single enemy? That tradition continues with Metal Gear Solid: Rising, set to be released next year.
Konami confirms that the no-kill is possible with Rising and hints that there may be Achievements for those that make it to the end of the game without taking a life. IGN says that you can opt to slice an enemy's weapon instead, causing them to run away. If you do manage to cut off a few fingers in the process, know that you will be forgiven. Also know that mechs are fair game -- just don't kill humans.
I'm betting that this will be the most stressful experience ever.