By FAR, the best fighting game ever made. Diverse and memorable characters, beautiful graphics, a fighting system that's intuitive enough for newcomers to pick up and play right away, but deep enough that you'll still be discovering new moves a year later. This game is awesome in every regard. Even people who usually don't care for fighting games seem to enjoy it.
Soul Caliber II has been out for a while, so you can pick one up for $40 now.
Even better, go buy a reconditioned Dreamcast platform for $30 and the original Soul Caliber game, used, for $20.
My Soul Still Burns!