To Zanarkan
Suteki Da Ne
(^Gee, on everyone's fav list.)
Challenge
Seymour Battle
Aeon Battle
Final Battle (whatever the Yu Yevon boss music was)
Otherworld
Silence Before the Storm
Brass de Chocobo
Yuna's Theme
Tida's Theme
The Deceased Laugh (any variant of Seymour's wicked theme)
The Prelude (All techno-fied!)

Probably more, I can't remember all the names off-hand.

Really good soundtrack, even though Uematsu got lazy.