Totally random list below. Each one mentioned is famous in his or her own right, but not for being great guitarists. Feel free to mention some more in the Comments thread.
Not that he needs more recognition for his greatness. Still, I was listening to his album of ancient folk songs, World Gone Wrong, the other night, and was struck by his style. Raw, bright, thorny, and very thought-out.
Mother Maybelle Carter
Few things get me as riled as seeing Mother Maybelle Carter's left off every new "Greatest Guitarists of All Time" that gets published. She wasn't the flashiest player in the world by any means, but she was, quite possibly, the single most influential guitarist ever born in the U.S. Where can you hear her influence? When any kid picks up an acoustic guitar for the first time and learns how to strum what they've just learned from some Mel Bay chord book.
Lou ReedWhen most people think of "Lou Reed" and "guitar", they think of the classic opening to the live version of "Sweet Jane" on Rock and Roll Animal. However, Lou's not the one playing those chords. Like Mother Maybelle, Lou isn't the most technically adept player. But few songwriters of his stature pay such close attention to tone. Not does his guitar work sound good, he chops out his chords with a weird balance of airy looseness and rigorous stiffness.
Isaac Brock of Modest Mouse
In the last week, I've heard at least three bands on KEXP whose songs featured wonky, rubber-band guitar solos. Not one of those bands was named Modest Mouse. While Johnny Marr has been the reason most people mention "awesome guitar work" and "Modest Mouse" in the same breath, frontman Isaac Brock's spastic string strangulation and cracked-out chop-funk rhythms are the main reason the Mouse is so unmistakable. He's toned it down a little since the band got more famous, but I did hear that vintage Brock sound when the band played "Satellite Skin" on Letterman last week. Here's hoping he winds his way back to his roots.