I wonder why marieusagi didn't rate well on concept. IMHO, di3s3l_666 and marieusagi both seem better as to the concept of the ninja, which is utter concealment. NDX's looks too muscular, much like a superhero. And it's too bright a background. Marieusagi, although not heavily shrouded in darkness, does have the prerequisite weapons, and as per my description of ninja and kunoichi, is nearly impossible to tell male from female. Is it a thin man with long hair, or a muscular woman with a tough-looking eye scar?
I guess the variety of entries is making the voting for concept pretty difficult (since we got a gun ninja, superhero ninja, ninja ninja, and not-really ninja). They're all fairly striking.
But enough excuses, it definitely has to have a silencer.
But... if a ninja fires a gun, and there is no-one left alive to hear it, does it make a sound?
I think it works better without, personally. Kind of like, "I can be right next to you, kill you, and don't even need to hide myself to do it". Otherwise he might as well have something properly subtle like poison or at least a sniper rifle?