MechAssault: Phantom War Codes -

Cheat mode:
Finish the game with a 100% completion to unlock the cheats after the credits.

Ragnarok Assault Mech in multi-player mode:
Play the "Divergent Entry" mission. Climb the wall to access the second area. Look to the right to find a locked bunker. Use the access terminal on the left side of that bunker to play the hacking mini-game. Complete the game to unlock the bunker, which contains the Ragnarok Assault Mech. Use that mech to complete the level to unlock it in multi-player mode.