What Illustration Can Be - Christoph Niemann
I can't think of another single Illustrator that is remotely similar to Christoph Niemann. He has such a wide range of styles all showing a high level of craftsmanship. The first words that come to mind are unique, smart and humorous. It seems like he's comfortable in any Illustration style and chooses whichever style best fits the project at hand. Check out his blog Abstract City and his personal site.