I've loved Skottie Young's style since I first saw his work in New X-Men. When I contemplated buying a graphics tablet, I watched his Youtube videos over and over. In an industry of perfect looking super heroes, his work is unique. It's not posed or focused on anatomy, it's exaggerated, loose and active. No one does this style better.
He updates his blog daily with a new sketch based on whatever geeky subject matter comes to mind, adding to each a personal story of why he chose the subject and how he feels about the outcome. And he's been on a roll lately with some awesome pieces like his Bone sketch and the gloomy version of X-23 below. Don't forget to follow his blog for new ones every day.