Dave MacIssacs is incredible, but does he really fingerpick, or just flatpick faster than thought? Good thing that someone mentioned Tony McMannus, Chris Proctor too.
How about Stefan Grossman, Phil Keaggy, Richard Thompson, Woody Mann, Ken Perlman, Preston Reed, Muriel Anderson, John Hammond, Mark Hanson, Rory Block, Rick Foster, Martin Taylor and Dale Miller. Getting further away from standard tuning are Adrian Legg, Pierre Bensussan, Martin Carthy, Marcel Dadi, and of course, Michael Hedges. Oh, I guess none of them are "commercial".