Martin Bulloch from the band Mogwai, in my opinion, is a very underrated player, especially in the post rock, shoegaze genre. A lot of drummers in this genre or similar genres overplay their instrument and are frequently more talked about.
I'm a big fan of Gary Novak's playing, and I'm dropping his name whenever I can. I'm not sure if he really is that underrated. In fact, this under-/overrated thing can be quite subjective and experienced differently depending on the people surrounding you everyday, and the information you personally receive through the internet, tv, music etc.
Male - Rob Dimaggio. He plays on the George Lopez show. I saw him at a clinic and he played EVERY style well. http://www.youtube.com/watch?v=7n4s9NXRJmA He's originally from France but don't hold that against him.