Disclaimer: This doesn't mean that the mangaka I listed here are OK for all Christians. Everyone to their personal convictions.
Watsuki Nobuhiro (Rurouni Kenshin, Gun Blaze West)
Great artwork in RK, especially Vol 11+. His latest manga, Busou RenKin is a little.....strange though.
Kazuya Minekura (Saiyuki, Bus Gamer)
Angsty cool bishies in a fallen corrupted world, enuff said.
Warning: Some titles are ai-shonen and it's not uncommon to see bishies with exposed chests and unzipped pants.
Kubotite (Zombie Powder, Bleach)
Supernatural stuff + the punk style.
Kentaro Yabuki (Black Cat)
Hiroaki Samura (Blade of the Immortal)
Great art + old Japan + fight scenes + emotions that go with it.
Warning: Expect much violence and blood.
Gosho Aoyama (Detective Conan)
Yukiru Sugisaki (DNAngel)
Not really crazy about his story-telling but the art is crazy gorgeous yet clean