I don't know of any songs that were written specifically for a baritone guitar. And whether or not you use a guitar like that is going to depend, in large part, on what your vocal range is. I bought a baritone because there were several songs I wanted to play that felt just too high for my voice, yet didn't sound quite right transposed into another key or with the guitar capo'd up. Sometimes a baritone just hits that sweet spot. But everyone's sweet spot is going to be different.
