I would say Tifa’s theme did it for me. After hearing it, I was all like, "K-Mart. Definitely K-Mart." If you were there, you would have slapped me. I actually fell asleep while I was in Midgar.
FFIX had some great character themes as well. In particular, I like Vivi’s Theme, Jesters of the Moon (Zorn and Thorn’s Theme), Zidane’s Theme, Cid’s Theme, Quina’s Theme, Freya’s Theme, Garnet’s Theme (a nice version of Melodies of Life), and Rose of May (Beatrix’s Theme).