Now are we talking underrated or underpublicized? These days with all the guitar mags and web stuff you see deserving guys getting great reviews for their playing and I assume that would lead to record sales in the guitar community. But if we're really talking about guys who are semi famous to guitar players, but not so well known to music fans in general, there are a lot of guys, and girls that spring to mind.
David Grissom - played with Joe Ely, James McMurtry and John Mellencamp, and recently with Storyville...this guy is always dead on.
Chris Duarte - His strings are big, his amp's gonna blow up, and he wears red Chuck Taylors...what the hell more do ya want?
Susan Tedeschi - really cannot say enough about her. See her live and you will know that although girls are cool, girls with guitars are cooler, and girls who beat the crap outa those guitars while soloing are the coolest.
John Hiatt and Warren Zevon - although known primarily as songwriters, these guys can each play a pretty mean guitar.
Gatton and Buchanan are dead, so my vote for the current "humbler" doesn't even play a tele. Tuck Andress's fingerstyle jazz chops are dropjaw and always supremely musical.
I'm sure I'll think of tons more...
Let's see....Vinnie Vincent and Micheal Angelo...just kidding!
Please don't put CheezIts in Daddy's amplifier.