I would have to say The Violinist of Hameln.  The character
design is beautiful, the characters themselves are rather
interesting, and there are so many scenes in those 26 
episodes that I want to own!
The story itself is beautiful and really draws you in...
The search for Pandora's box to unseal the demon lord, 
Chestra... the power lying within their children, Hamel, a 
half-demon, and Sizer, a half-angel. The twist is that the
demon son grew up around humans while the angel daughter
 was raised
amongst demons... their lives an eternal struggle for and
against fate.  ^_^