If you need help in the game then try entering the following codes at the 'Main' menu. If you have entered the code correctly you will hear a confirmation noise.

Unlock ALL Special Moves:
Press Left, Left, Right, Right, Left, Right, Left, Right.

Unlock Infinite Weapons (except Batarangs And Electric Batarangs):
Press Y, X, Y, X, Left, Right, Left, Right.

Unlock Infinite Batarangs and Electric Batarangs:
Press Left, Right, Y, X.

Unlock Infinite Batcuffs:
Press X, Y, X, Y, Left, Right, Right, Left.

Infinite Batcuffs:

Enter the following at the main menu (X, Y, X, Y, Left, Right, Right, Left)

Special Moves:

Enter the following at the main menu (Left, Left, Right, Right, Left, Right, Left, Right)