Leo Kottke's the man. Check out any of his material but particularly the earlier stuff before his right hand got injured. A master of the 6-string he's probably best known in guitar circles as THE top 12-string virtuoso and his slide playing's pretty awesome. He can play chords, melody and bass lines simultaneously, at high speed and with a real beefy sound... and not a single effects pedal in sight. Anyone's who's a guitar fan is advised to check LK out, though you might decide to quit playing once you've heard ' 6 & 12 string guitar.