Originally Posted by Volatar
Well, according to TVTropes...
(Byakuren, Nue, Kogasa, Kaguya, Parsee, Rinnosuke, Sara, Yuuka, YuugenMagan and Yumemi). But that page could perfectly be renamed as "Characters without any kind of hair adornment, hat or not". Because for example and as far as I'm aware, Sanae doesn't wear a hat, and I don't see her listed there.