Hello all.
My most favorite mangaka is probably Yamamoto Kana (Di[e]ce, Togainu no Chi [Yamamoto Kana Version] and also drew several doujinshis for Prince of Tennis, Eyeshield 21 and Katekyoushi Hitman Reborn!), for her gorgeous art and all the emotions that she conveys with her storytelling. I also own several of her manga in print and am planning on buying more as more is available to me even though I don't understand a single word of Japanese.
Another great mangaka is Yumeka Sumomo, who's artwork is so simple, yet beautiful and whose bittersweet stories are usually always touching, and sometimes a little bizarre and stimulates thinking.
Furthermore I also really like the art of Obata Takeshi, Yuki Kaori and CLAMP.