My fave has to be Ballad of the Goddess, not just because I learned how to play the basic melody on the flute... But cause it's freaking awesome!
I love Groose's theme because it reminds me of the theme on Tetra's Pirate ship from Wind Waker. I love the nostalgia!
I love Fi's theme at the end, since it's sad and fit perfectly for her, and I also love the Song of the Hero, since it also shows up in Wind Waker, during that little opening bit where it talks about the hero of time...
F'it! LOVE ALL THE SONGS!