I am suggesting a new badge entitled
Ninja. This would be a gold badge. And in keeping with the secrecy of true Ninjas, the badge should not be mentioned anywhere except a user's profile page (and after implementation, delete this request to protect that).
What are the requirements for awarding the badge? Well, it would be a subjective badge to which the SE staff would award said badge to the user in question based upon their contribution to either the community or SE in general. Basically, if a user goes above and beyond, or makes a significant back-channel contribution to the community, they can be deemed ninja-worthy.