Puyo Puyo! 15th Anniversary Cheat mode
At the title screen, hold L + R and press Up, Down, Right, Left, X, B, Y, A to unlock all bonus characters, rulesets, and additional settings. If you entered the code correctly, you will hear a sound and the main menu will appear.
The image featured at the top of this post is ©The Legend of Heroes: Trails of Cold Steel III key art / Original