Erm, well… here are my top 5. Note, I’ve only played BB:CSEX so if there’s tracks that were exclusive to previous versions, I may not have heard them.
#1: Soukyuu no Hikari - This one’s really epic, especially when used with Jin (my main atm). Besides, I’m always a sucker for game opening songs.
#2: Blue Beating - This is what I’d like to use in training, but it’s not available… DAAMMMIIIIT ISHIWATAAARRRIIII!
#3: Motor Head. Since I don’t get to use Soukyuu no Hikari that often, I usually go for this song. That engine strumm… just… HNNNNGGGGG!
#4: Howling Moon: I admit, I don’t use Valkenhayn or Rachel, but I like the former’s theme more so than the latter (in fact, I don’t really like Rachel’s theme much).
#5: Lust SIN - I’m a Jin main, so it’s a wonder why this isn’t higher. The answer is thus: THIS THEME IS NOT FIT FOR ME WHILST IN JIN’S SOUL! Yet, compared to the rest of the soundtrack, I like it enough to put it in my Top 5.
Honorable mentions are Alexandrite (which I loved the first time I heard it, but… sad to say Squirrel Buns is a real ditz and a complicated woman), Condemnation Wings (love the song, hate the owner), and SUSANOO (Hakumen’s awesome looking, his song’s meh, but he’s just so goddamn complicated to play).