The Metal Gear Solid titles, of late, have been trying to do that, and I bring it up to mention an annoyance. One of the levels has the objective of getting through without killing anyone (or something similar to that). However, at the end of the level, if you complete this objective, you fail to get a certain bonus because you didn't kill everyone. Argh. So in following the objective, you get fewer points. And, as I remember, there isn't any penalty for failing that objective. Very irritating.