A crossover fighting game for the PSP, featuring FF characters as far back as FF1, the current roster goes as
Title/ Hero/ Villain
Final Fantasy/ Warrior of Light / Garland
Final Fantasy II / Firion / Emperor Palamecia
Final Fantasy III /Onion Knight / Cloud of Darkness
Final Fantasy V/ ? / Exdeath
Final Fantasy VI /?/ Kefka
Final Fantasy VII /?/ Sephiroth
Final Fantasy VIII /Squall Leonhart/ Ultimecia
Final Fantasy IX /Zidane Tribal / Kuja
Final Fantasy X / Tidus / Jecht
Presumably the hero for V will be either Bartz or Lenna, and probably in the Mimic Class (potentially most powerful class in the game), VI will have to be Terra, VII will probably be either Cloud or Jack.
Game features a control scheme along the lines of
Triangle: environment interact (Run on walls, slide on rails etc)
Square: HP damaging attacks
Circle: comboable Brave draining attacks, the more 'brave' you have, the more damage your HP attack does
X: Jump, most characters feature a double jump and some a triple jump.
R+X: Quick Dodge
With matches taking place in a 3d environment.
Also includes a mode called EX force, which is triggered upon gaining a random drop item. This works kinda like the Final Smash balls in SSB:Brawl, putting the character into an empowered state (seemingly some have more than one, I'm not sure how that works), for instant Zidane and Kuja go into Trance mode, Terra would go into her Esper form, etc.
One goes into this state by filling up the EX gauge (presumably the item fills it), and pressing X+.
While in this state, the character, upon landing a combo, will engage in an EX burst special, basically consisting of the character's signature Limit Break/equivalent, i.e Tidus goes into his Blitzball/Sword combo that was his final Ultimate in FFX.
Characters will be customisable to a degree by using purchased weapons and equipment (bought with Gil earned), as well as levelling up.
It has been stated that there will be at least 20 characters upon release, with the possibility of hidden characters. Each character will have a story mode, and beating all of them will be needed to view the games full storyline, which so far seems to involve Chaos, God of Darkness, and Cosmos, Goddess of Light.
Wiki page here http://en.wikipedia.org/wiki/Final_Fantasy_Dissidia
Trailers can be found here http://www.gametrailers.com/game/5024.html