This is a shisa (lion-dog) on a traditional roof on Taketomi Island. Pretty much every house in Okinawa has a shisa (often two -- a male with an open mouth, and a female with its mouth closed), either on the roof or on the gateposts to ward off evil spirits. (I have a pair on my gateposts, too :-))

I should add in response to a comment below that shisa have become a symbol of Okinawa and are sold in every possible form, from stuffed animals to vases to works of art. Even the ones on houses aren't really scary any more, but rather can be cute and quite friendly looking. Many of them are now meant to make you smile, not frighten you away! For an idea of the variety of shisa styles in Okinawa, go to http://community.webshots.com/album/15423935raakrXiwuP and http://community.webshots.com/album/26034191RABKZbEFXw.