5 cheats:
For the following cheats you must be facing 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 inventory then to the flares press and hold F + I + R + E.