MLB 08: The Show
All classic stadiums
At the main menu, press Down, Right, Circle, Square, Left, Triangle, Up, L1 to unlock all classic stadiums. If you entered the code correctly, the controller will vibrate. It will not show up on your profile, but it does work in Exhibition mode.
All Golden and Silver era players
At the main menu, press L1, L2, Square(2), Triangle, Circle, Down to unlock all Golden and Silver era players. If you entered the code correctly, the controller will vibrate. It will not show up on your profile, but it does work in Exhibition mode.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art.