Disgaea 4: A Promise Unforgotten Cheats

Unlock Classes
Android: Beat the main game and start a 2nd playthough
Archer: Healer and Valkyrie level 15
Armor Knight: Warrior level 20
Beast Master: Warrior or Valkyrie level 15
Gunner: Thief and Skull level 15
Lady Samurai: Valkyire and Archer level 30
Magic Knight: Warrior or Valkyrie, and Skull or Witch level 30
Masked Hero: Thief and Warrior level 25
Ninja: Thief and Skull level 30
Onmyo Monk: Sorcerer and Ninja level 30
Professor: Healer and Sorcerer level 20
Sorcerer: Skull and Witch level 15

Endings
Meet the following requirements to view extra endings.

Axel Ending: Lose to Axel when you fight him in Episode 6.
Desco Ending: Lose to Desco when you fight her in Episode 3.
Desco's Epilogue: Set Desco as Valvatorez's Stepsibling in the Legendary Tree evil symbol.
Emizel Ending 1: Lose to Emizel when you fight him in Episode 1.
Emizel Ending 2: Lose to Emizel when you fight him again in Episode 2-.
Emizel's Epilogue: Set Emizel as Valvatorez's Rival in the Legendary Tree evil symbol.
Fenrich's Epilogue: Set Fenrich as Valvatorez's Comrade in the Legendary Tree evil symbol.
Fuka Ending: Lose to Fuka when you fight her in Episode 2.
Fuka's Epilogue: Set Fuka as Valvatorez's Mentor in the Legendary Tree evil symbol.
Postgame Epilogue: Complete Extra Battles 1, 2, 3, 4, 5, and 6 in postgame.
True Final Battle: Defeat the normal final boss with Valvatorez at level 500 or higher.
Vulcanus Ending: Lose to Vulcanus when you fight her in Episode 5.
Vulcanus' Epilogue: Set Vulcanus as Valvatorez's Lover in the Legendary Tree evil symbol.