Hotel Lobby -- Utada. Likely my favorite song of hers in English (outside of KH work which is pretty untouchable), because the message is just unexpected and written a bit abstractly on top of a fairly neo-happy beat.
Just before that: the "Fukanzen Nenshou" single EP by Chiaki Ishikawa, which holds the songs Fukanzen Nenshou and Switch ga Haittara.