In no particular order, here we go:
Mike Mignola (Hellboy, BPRD, Lobster Johnson, etc.), Linda Medley (Castle Waiting), Evan Dahm (Rice Boy, Order of Tales, Vattu), Nicholas Kole (The Dawngate Chronicles-webcomic), Murata Yusuke (Eyeshield 21), Samura Hiroaki (Blade of the Immortal), Inoue Takehiko (Vagabond), Aki Irie (Ran to Haiiro no Sekai), Peter Bergting (Domovoi, The Portent, currently on Mignola's Baltimore), Eichiiro Oda (One Piece) and Enrique Fernandez (L'isle sans sourire, Aurore, Brigada).
My favourites cast a pretty wide net in terms of style. For example, I love Mignola for his stripped down, simple style with heavy, blocky shadows and excellent composition (expecially when it comes to cover illustrations) - but I like Aki Irie and Murata Yusuke for their super-detailed, super-expressive style. Inoue Takehiko is a master of the black and white - while Enrique Fernandez is brilliant at coloured work.