For some reason, Yu Yu Hakusho instantly popped into my head. But then I remembered about Hiei and Kurama, and they're definitely bishounen. I agree about One Piece, definitely. From what I've read, which isn't much, there aren't any bishie-looking guys there. Uh, how about Dragon Ball? o.o;;
It depends on the art style used and the genre of the anime/manga. So, something like Dr. Slump or Bo-Bo-Bo-<insert the rest of the Bo's here> are unlikely to have any bishounen. But I might be wrong, I haven't read much of those manga.