Okay, here's my list (I tried to do them in order of preference as much as possible):
Perfect Blue
Ninja Scroll
Vampire Hunter D
L.I.L.Y. Cat
Audition
Battle Royale
Demon City Shinjuku
Wicked City
Oldboy (I'm with Chrono here!)
Paprika
Imprint
Legend of the Overfiend
Death Note
Vampire Hunter D: Bloodlust
Tetsuo: Iron Man
Death Note II: The Last Name
I think if you're looking to expand the list, I don't think you should try to include exploitation but to expand to horror series. Since anime series are such a staple in Japan, a lot of exceptional horror are in these series and I think they should definitely be considered.
My anime series list:
Gantz
When They Cry
Elfen Lied
Berserk
Death Note
Boogiepop Phantom
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