Guilty Gear Codes -

Alternate colors:
Press Square, Triangle, Circle, or X at the character selection screen.

Hidden difficulty setting:
Hold Square + R2 + L1 + Down at the PlayStation logo, and keep the buttons held as the game loads.

Fight as Testament or Justice:
Successfully complete normal mode as any character.

Fight as Baiken:
Successfully complete normal mode with Sol or Ky. Baiken will appear after the credits. Defeat her to unlock her in versus and training modes. Note: Baiken is very fast and very cheap.

Fight as Bosses (Japanese version):
Press Down + Square + L1 + R2 at the Arc System Works logo. Release the buttons when the phrase "Team Neo Blood" disappears. Testament, Justice, and Baiken may now be selected in versus mode. This also replaces the "Normal" mode with "Hard" mode.