I love Masami Yuki's style, particularly the way he draws clothes (especially tucked shirts) and hair (shiny).
Hiroaki Samura is my favorite character designer. I like how he's able to make very ugly characters beautiful and very beautiful characters off-putting.
Aesthetically, Takehiko Ito takes the cake. Clothes, spaceships, weapons and technology, vehicles... incredible facial expressions and colors, too. He's good at making his messy style look clean. (Whoever did the coloring for the Outlaw Star anime also deserves an award).