It was almost to hard the choose, so many came to mind. ( ^ u ^ )
But I narrowed it down to my king Ulquiorra Cifer. :D
Who is a Arrancar.
If I remember correctly (correct me if I am wrong) arrancars are created from hollows that have teared off their mask gaining similar powers of a soul reaper.
The Hogyoku to grant them even more power than before.
Even though there is plenty of more arrancars to choose from, Ulquiorra will always be my favorite cause his resurreccion form is favorite, and he hot af. -3-