Black Rock Shooter / Vocaloid buttons.
Bah, there's no substitute for bad lighting. *shakes Photoshop*
Its not framed as nicely as the other ones...
I drew the chibi Hatsune very circular on purpose, and hastily made my other Hatsune into a button. Everyone liked the non-chibi one more, but it's one of my absolute favourites. :3 Its that bright pink!
Buttons available here Available here [link]