Select level:
Press r, l, up, down, and b in the main menu
Jump level:
Press r, l, up, down, a, x, click on the right analog stick, b, a, b, a during the game. You will complete the level immediately with the “Silent Assassin” qualification.
God mode:
Press r, l, up, down, a, r, l, black, white during the game.
All weapons:
Press r, l, up, down, a, up, x, a during the game.