For the following cheats you MUST be facing ABSOULTE NORTH!

Level Skip:
Go to the inventory and then to load game press and hold L + I + F + T.

All Weapons:
Go to the inventory then to the large medipak press and hold C + T + R + L.

All Items:
Go to the inventory then to the small medipak press and hold A + L + T + G + R.

God Mode:
Go to the invetory then to the flares press and hold F + I + R + E.

Thanks to Revolution reader richard hennesy!