Your eyes do not deceive you, that *IS* a t-shirt with a chibi version of Rorschach, with a bloody butcher's knife that says "Need Help?" underneath. Incidentally, that noise you hear is the sound of Alan Moore of rolling around in his yet un-dug grave.
I've seen it a couple of times before, but the last time I was there, I decided to snap a picture of it with my (incredibly lame) cell phone camera. The store in question is New Yorker. I tried looking around their catalog for a better photo, but they don't seem to have one. It wasn't the only one of this kind, as they seemed to have others with horror-movie characters (all of them chibi-ed), such as Freddy, Jason, and the puppet from Saw.
I have a very strong suspicion that this is not exactly legally licensed material.