I hadn't put much thought towards a favorite RPG writer.
Having given it some thought- the easy answer is Paul "Wiggy" Wade-Williams. I think I'm fortunate in that it seems my obsessions mirror his in many ways. I love the way that guy's mind thinks! Also, I cannot keep up my reading with the rate at which products come out from Wiggy.
Triple Ace Games is one of my favorite companies and occupies a lot of my shelf.