I watched the Gunsmith Cats OAV a long time ago. The manga might have been different but it didn't have nudity. The majority of manga and anime are no more different than the American "Superhero" comics which will feature very big chests and very little skin.
In fact I stopped reading American comics when one comic featured a jay-naked Bush sobbing & surrendering at Magneto's feet.
Ultimate X-Men, right? I'm not a huge fan of that series- they've basically made the X-Men a bunch of angsty nihilists.
The new Captain America in the Ultimates is pretty cool, though.