I'd like to hear someone sing Johnny Cash's "Folsom Prison Blues" in a slow mournful style, with an acoustic blues guitar arrangement, rather like the way David Bromberg performs Dehlia (click to play). (I'm not sure the link will work; if not, go to Yahoo! Shopping > Music and search for DEHLIA.

Keb' Mo' does something a bit like what I had in mind on the various artists' CD Kindred Spirits: A Tribute to the Songs of Johnny Cash.