Soul Calibur get's my vote. I like the simple raw sound that it has compared to the other games.
And I was excited it was gonna be DLC but it doesn't include Eye to Eye, Blade to Blade (imo, the best track in the entire series) so that's kind of a deal breaker for me, not worth it now.
Bayonetta, Dante and Lightning are all amazing choices, I'd be most stoked for Lightning.
Love or hate XIII, Lightning is a bad *** character.
But if I could pick anyone, I'd love to see Squall. I would geek out like a school girl if he was in.