Final Fantasy Explorers
Final Fantasy Explorers' Trance mode is a powerful asset. Not only does it allow you to summon the Eidolons you've defeated, but it also lets you transform into 11 characters from the series and utilize their ultimate attacks.
The chart below (click on it for the full image) details each characters' special move, from Cloud's Omnislash to Terra's Riot Blade, and you're going to want to use them all throughout the course of the game.
Final Fantasy Explorers comes out for the 3DS on January 26.