Project X Zone
Anyone else picked this up yet? I'm only a few chapters in but so far it's just as awesome and crossover-tastic as I'd hoped. The battle system is simple, but fun, and watching all the characters interact makes the fangirl in me happy.
My only real complaint so far is that it seems to be somewhat light on strategy for a strategy RPG, but the Valkyrie Profile-like battle system is fun enough that it doesn't really bother me (yet.)
I definitely recommend picking this up if you have a 3DS.