I think Phoenix is the most famous of his unfinished works... but how many Tezuka mangas are unfinished... and what's the reason why?
So far I count:
-Phoenix
-Vampires
-Dororo
-Ludwig B
Obviously Phoenix was left unfinished with Tezuka's death, but because it's such an on again off again project, with self contained stories, we the readers aren't really left hanging.
For Vampires, the series is actually split up into Vampires, and Vampires 2: the Sequel. The Vampires story itself ends after 3 volumes, but Vampires 2 is left hanging on a cliff-hanger ending after just one volume. I'm pretty sure that the reason for this was that the magazine that Tezuka was being published in went under.