Spartacus: Legends - a free-to-play fighter (with loot drops) on XBLA is out.
I played just a little. Fighting the AI is kind of fun, and there is an attempt to differentiate itself from other fighters, though I'm not sure yet how deep it is. I was excited until I took it online, at which point the net code proved to be unplayably laggy.
Online, I had one queued fight, which was evenly matched; the next was a Quick Match, which apparently doesn't take level-balance into consideration-- my gladiator was slaughtered outright by a vastly higher-level player. So it requires silver coins to revive him. Gold coins appear to be the not-free currency, though I may have gained a couple of those by leveling up or something.
It's from Kung Fu Factory, you all remember them; they're the ones who made Supremacy MMA and Hello Kitty Seasons.