Air Gear (The art is gorgeous!! Best drawn action series)
Nana (Ai Yazawa is soo talented

)
H2O (I read this one recently and the art's really pretty, especially the girls

)
Veritas (best drawn martial arts manga ever and Vera and Madoka are drawn beautifully)
Rockin' Heaven (Just another of my favourites.

)
Katekyo Hitman Reborn
Bakuman ( Takeshi Obata is one of the best artist out there)
Naruto (the art is not bad but isn't really great either and it has really dropped quite a few notches in the recent chapters but unlike many other shounen manga, Naruto's art is clear like in, you can actually understand the action panels)