Henrique Pinto (homonym of a famous guitar teacher here), who is actually a student of luthier course from Tatui's Conservatory in Brazil, where Edson Lopes teaches guitar, has just made his first guitar, and he decided to build it with paper. He had prior experience with paper, he used a technique we call "papietagem" or Papier Collé (I don't know the English word). He said he spent 3 years to develop the technique before starting to build the guitar. Some parts of the guitar are made of regular wood, like the scale. But soundboard, back and sides are totally made of paper.
Sound is quite nice for the first guitar of this kind. Here Edson Lopes trying the guitar at youtube: