For sure Bill Frisell...the guy has done it all from his own solo stuff (Gone Like A Train is brilliant) to industrial insanity with Zorn's Naked City (a la Torture Garden or Leng Tche)

Frisell did a disk with Vernon Reid you don't often hear about: "Smash and Scatteration" -- very interesting.

Don't miss John Mclaughlin

Shawn Lane with Hellborg is great

Mick Goodrick is great but hard to locate

George Benson from way back in the 60s before he went soul/pop -- that guy is a monster (or was?)

But aside from just guitar stuff...essential recordings include Cecil Taylor's amazing piano playing, Dolphy and Coltrane on sax, Miles Davis, Bill Evans, Cannonball, Monk, etc...