A Visored (from Bleach). I don't like them existing outside of the anime, because people tend to make their characters Visoreds, because they want them to be brutally strong. Lol. Visoreds have epic masks... au I could go to a costume party as an Arrancar.
zaidi likely, I'd just go as a Shinigami, as I have the cosply outfit, with the Captain's haori.