Unlock it All:
At the Stellar Cartography (mission select) Screen, press Up, Left, Down, Right, Up, Right, Down Left, Up, Then press both L1 + R1, Then press both L2 + R2. If the code is entered correctly, the screen will flash and "CHEATS ON" will appear below the mission name. By pressing Left or Right, you will choose any mission. To activate the Cheats, pause the game, then go to the Cheat Screen, then highlight the cheats and press X. You can choose from one-hit kills, invincibility, and all weapons.

Play Credits Movie:
At the Mission Briefing Screen, press Left, Right, Up, Down, Left, Right, Up, Down, Left, Right, Up, Down, Left, Right, Up, Down, Left, Right, Up, Down. If entered correctly, the credits movie will automatically play.

Thanks to Revolution reader emperorshaun!