I get that the young professional generation wants to be able to define themselves. We all did when we were early in career. But Ninja? Really?
It may be that part of that self-definition, for many, includes coming up with trendy job titles. And it may be a function of my age, but I find it a little bit annoying. I'm not sure if it's the need for attention or a cooler-than-thou attitude of some people. But it just bugs.
And from a career standpoint, for all of the trendy flash of the titles, they aren't really a great idea. First, when a recruiter is looking for a person with a specific type of background, they may use possible titles as keywords. There may be a few, separated by "OR": ("program manager" OR "project manager" OR "development manager"). Yeah, nobody is really going to look for a "product ninja." If they use any variation on titles in their search, you are out of luck. And even if you aren't looking for a position at the time, recruiters should be part of your personal network for future career changes.
I get that sometimes a specific position may be challenging to describe. I struggle with this myself; "staffing manager" gets me calls from agencies, "program manager" leads people to believe I have technical skills. "Training manager" won't work because it's what I am doing now but not really "what I do." But I'm just guessing that "Ninja of awesomeness" isn't really going to help.