I'm tied between these 3
Reoko-sama from Bubuki Buranki
Because Reoko-sama is Reoko-sama, there's no other reason. I was going to pick Shizuru, but Reoko-sama won the spot this time.
Yoruka from Saijaku no Bahamut
"The traditional clothing, classic black hair and fancy hair ribbons are the way to go!"
She's voiced by Stella's VA and I love her high pitched voice. She is surprisingly not flat chested and she has the right Beef Meet size~ Erhmm... yeah...
Koito from Musaigen no Phantom World
Casually wearing headphones on her neck, Koito's fashion isn't really that common in the amine world. With her attitude changing in the middle of the series, that was the right time to take a fancy on her, plus that emotionless yet kind personality tops it all off.