That's the great and tragic Roy Buchanan, once introduced as "the world's greatest unknown guitarist." He never did become very widely known, but he was certainly admired, respected, and influential. I reviewed the double-CD collection Sweet Dreams here a few years ago...well, over seven years ago...and for further information, and an opinion which hasn't changed, I'll refer you to the two separate entries for disc 1 and disc 2.
And for this post, I don't think any assortment of individual YouTube clips would serve any better than this Austin City Limits appearance from 1976. It's thirty minutes long, but you'll know after four or five if you want to hear/see the rest.
I bet those two guys sitting right in front of him are guitar players, or trying to be. I still sort of wish he had played something other than a Telecaster, which has a brighter and thinner tone than some other guitars, or at least it usually sounds that way--it's traditionally associated with country music. But that was the tone he wanted, obviously.
For more information about his life and career, see the Wikipedia entry.