Sometimes, particularly with explosive or stun weapons, it can be difficult to tell whether your shots are actually hitting or doing damage. It's particularly bad when, say, you drop a grenade next to a victim, it explodes, and the cretin's still standing there like nothing happened. Did I hit him and he survived? Did the game not register a hit when it should have? Or did I simply miss?
If possible, and not too much trouble, I'd like a bit more obvious an indication that the victim's been hit. Maybe a wincing or doubling-over-in-pain animation? Possibly a sound cue? Hearing my enemies screaming in pain is always satisfying, but it currently only occurs upon their death.