I couldn't resist this older thread. Whenever I hear "unknown" or "under appreciated" guitarist I always think of Danny Gatton. Basically because he is (was) a Telecaster monster! (With an old Tele there is no hiding behind humbuckers and distortion.)

And because he was an un-schooled, play-by-ear guy. Tone, speed, extreme technique, creative, multi-style, musical, fun to listen to and tasteful. But I don't think he is appreciated outside of guitarist's circles.