Christy Doran played purely accoustic (classical, I think) guitar recently at Jazzfestival Willisau with Swiss bassist Heiri Känzig's group (he played bass with the Vienna Art Orchestra in the eighties), featuring a swiss drummer (Fabian Kuratli) and a third string player, Mark Feldman. Quite nice stuff!
Wolfgang Muthspiel is another great guitarist playing accoustic, at least occasionally. I heard a live recording of his with the string trio Triology (two violins, a viola, I remember right) and then found the CD they did together (released on Muthspiel's own label). Nice stuff.
ubu