Persona 4 Cheats
Main Character's secret weapon
Defeat extra boss in Void Quest.
Naoto's secret weapon
Defeat extra boss in Secret Lab.
Yousuke's secret weapon
Find in boss' den in Mysterious Shopping Street.
After completing the game with the true ending and starting a New Game+, a new fusion section will unlock and you'll be able to fuse Izanagi-no-Okami, one of the best Personas in the game.
These are available only on your second playthrough or later. Death will sometimes hide within treasure chests. Chests containing Death will prompt you to pick between the choices to open or ignore the chest. If you choose to open the chest, you will have to fight Death. If you defeat him, he will drop the ultimate weapons.
Yukiko's secret weapon
Defeat extra boss in Yukiko's Castle.
Kanji's secret weapon
Defeat extra boss in Steamy Bath House.
New Game +
Finish the game once.
Kuma's secret weapon
Defeat extra boss in Opera House.