There are too many bangers around the entire soundtrack to pick just one favorite, and it's hard even just maintaining a Terraria soundbank of 100 songs.

That said: Reverie, Constant Conquest, Candles and Clockwork (Alpha), Kingside Castle

Starfall is my best friend's favorite, and listening to that got me through being separated.

Fan music: Universal Remission (Diverging Delicacies), Cleopatra's Cocktail Party (LOFAM 4)