To automatically unlock all reconnaissance reports in the game, insert the following code at the in-game cheats menu: 0ZNDRBICRA.
To unlock Authentic Difficulty, beat the game on any other difficulty setting.
To activate a Kilroy detector that will alert you when a Kilroy is nearby during gameplay, insert the following code at the in-game cheats menu: 4V35JZHQD6.
To unlock new characters for use in multiplayer mode, insert the following code at the in-game cheats menu: HI9WTPXSUK.