I believe Navarre, Hermann, and the MiB/WiBs explode when you knock them out, be it via electric prod or darts. But anyway, I don't think it would be much fun to play the whole game without killing anyone. Not that I favor wanton slaughter, but sometimes it can be annoying to get past certain points without somebody knocking an alarm or shooting at you.
EDIT: No, actually they don't. Navarre and Hermann can't be knocked out and the MiB/WiB don't explode if you put 'em to sleep.