I won't say who's "best," but I went to Allen Martin for a Bucks County rifle, and I've never regretted it.
Another name I will throw out there for you to drool over is Keith Casteel. He builds very ornate guns that are not everyone's taste (or just as likely, budget). I don't say he's the best, but he's worth a look, even if, like me, you're never going to buy one.
You really need to go to Dixon's in Kempton, PA, on the last weekend in July, find a builder or gun you like, and strike a deal. You will, however, have to be patient; I did have to wait five years. Now I did make the mistake of telling Allen not to hurry - never tell a builder that - but you have to figure that most well-known and respected builders have a waiting list.
Ask known builders on here like Mike Brooks, Roy Stroh, or Fred Lehto, or Matt and Toni Avance, or Matt Denison. The last two are probably shorter waiting lists, because from what I hear they simply build guns faster, but all have a line of customers waiting.