Hellboy seems somewhat popular, judging from references to it.

On the production side, it's pretty obvious from FLCL that some people at Gainax like Jamie Hewlett's work. Also, South Park. And reading Ghost in the Shell makes me think Enki Bilal was an influence on Masamune Shirow (witness especially the Russian diplomat woman). Möbius has done cooperative work with japanese artists, like _Icaro_.