It's reaaaally hard for me to pick just one favorite, especially with Cursed Leorina and Hyuponia already being spoken for (shakes fist), but I'll go with the only song that actually ever got to me emotionally:
I remember getting to where 1:49 kicks in and legitimately tearing up a little when I played it for the very first time.
My second pick would probably be either be The Sorrow Revives or Going to Lunatea, though. (Again, not counting songs that were already mentioned.)