One group of guitar artists that come to mind is the Hellecasters (Will Ray, Jerry Donahue, and John Jorgenson). Before I even knew of the Hellecasters I had met John Jorgenson at a guitar clinic in New Orleans. It was an afternoon clinic that I had heard about just after arriving in town on a Friday and the clinic was the next day. I made my way to the famous club Tipitina's and sat around the stage with a small group of guitarists. I was floored by his style and tone. I was fresh out of the midwest and had never heard anything like it. It was so authentic and tonefull. I had no idea who he was or was to become.
Afterward I got to spend some time talking equipment with him. He was very gracious and patient. I still own the Fender Lace pickups that he recomended to me and was playing that day. He told me that he had been giging with the Meters. Of course I had never heard of them and the thought quickly left me. Some months or maybe a year or so after that day I saw a performance by Elton John on the Tonight show, and guess what? John Jorgenson was playing in Elton's band and has been for some time now. Then I remembered that John said he played with the Meters. Turns out the Meters were like the founding fathers of funk in the USA. That in turn led me to the Hellecasters which are not like the Meters at all, but boy can those three guys play. Amazing!
If you haven't listened to the Hellecasters then you owe it to yourself to do so, but be afraid. Be very afraid because their playing will scare the pants off of you. It is hard to discribe their style except to say that it is essential listening for every guitarist with any ambition what so ever.