Full Metal Alchemist
Seconded.
I'd add Samurai Champloo, Cowboy Bebop, and Ghost in the Shell to that list. Also the Akira manga (I'm still kinda nonplussed by the movie). Oh, and Hellboy in some system that isn't GURPS. I hear they're doing the Girl Genius webcomic setting in GURPS too. I think there's a Trigun D20 somewhere out there.
Also, Bakumatsu Kikansetsu Irohanihoheto (can somebody please tell me what any of that means so I don't have to type it out any more?), Black Lagoon, and Code Geass strike me as pretty gameable.
Wanting to run a game based on FLCL is like wanting to fly. It sucks because you know you'd only hurt yourself trying.
Snow Crash is something I'd game in. Likewise Dune.
The DrMcninja webcomic is also something I'd play in.