With one condition. It can't be in the FF series. It can be from Sqenix (Square Enix), SEA (Square Electronic Arts), or plain-old Squaresoft, but no FFs. Me, I say Xenogears, an SEA production for the PSX. Several references to psychology (There's a character named "Id", for example), delicious religious over and undertones, and most importantly, mechs, known in this game as Gears. Other candidates were Star Ocean 2 (Second Story), Valkyrie Profile, and Earthbound.

