Tales of Vesperia. Tackling the game's Hard difficulty will be a blast if you have three players with you instead of putting up with the flimsy AI. Normal difficulty is mostly mindless, I don't recommend playing on it in 4P mode or you're gonna murder everything with your eyes closed, and the game's awesome battle system won't get a chance to shine.
"Hurry up and make me the star of the sequel!" - Super Zur confirms Guardian Heroes 2!