Mine is Farewell Hyrule King. I absolutely love this song. It's very moving and I can listen to it over and over again. Molgera battle and Outset Island come after FHK. Wind Waker had such an amazing soundtrack.
I really enjoyed the Ocean Theme, and Farewell Hyrule King [which is indeed the song from Hyrule Castle in AlttP]. I also liked the ending theme, it's probably my favourite in the game. It's between that and The Legendary Hero.
Runners up would probably be the Dragon Roost Island theme, the opening theme (where it explains the history of Hyrule and whatnot,) and the song it plays whenever Laruto (that dead Zora sage) appears; it was so sad but beautiful. Then again, it was essentially a remix of the opening theme.