On some boss fights in KH2, I played music that fit the battle. Here's a few examples:
1000 heartless: Me Against the World, Headstrong(Its obveuse)
Dragon Heartless: Butterfly(because it's Asian)
Xaldin: Ichirin no Hana(Hana is Japanese for flower, or the Rose)
Hades: Disco Inferno(FIRE!!!)...