All levels - At the main menu,enter X, Y, B, LEFT, UP, RIGHT, L TRIGGER, R TRIGGER
All weapons and Skip level - During gameplay(not paused)enter R,L,UP,DOWN,X,A,click Left Analog Stick,press B,A,B,A.If you enter this code in the training area a message will come up saying that you have achieved Silent Assassin rank.
It will quit the training.Go back into the training area and you will now have all weapons.