My absolute favorite song is Promise from Illuminations 2000
Others are...
All Fantasmic Music (I bought the DL soundtrack, Best soundtrack i've ever bought)
Illuminations ROE
Any Haunted Mansion music or loops
Yo Ho (A Pirates Life For Me)
Great Big Beautiful Tomorrow
and Its a Small World :lookaroun (I really do like it, it doesn't bother me if its stuck in my head LOL)