And here's the irony: A good half of the recently added hairstyles were, in fact, gender specifically designed for females:
I think it's actually a 50:50 split between male and female hairs for the type 0 ones. And I'd say Trey's and Nine's hairstyles are actually more popular among females than some of the female styles.
Truth be told, I don't think we have had "any" hair designed as unisex so far. The long braided ponytail and the pompadour were both runner ups in the hairstyle design contest in the male category and the prior is more commonly worn on women. I have yet to see the pompadour and afro worn seriously at all >_>