Select the "Credits" option from the main menu, then press X while the credits are being displayed.
Game Shark Codes
Master Code (Must Be On) ECB8C7E8 1456E60A
Infinite/Max HP 4CAD7FB2 14562A454CAD7FAE 14562A45
Infinite/Max AP 4CAD7FB6 1456089C4CAD7FB8 1456089C
Infinite Gold 1DBFBB00 144F25CC
Infinite Level Up Points 4C262AA4 1456E788
Max Sword Weapons 3CAD7FCF 1456E781
Max Axe Weapons 3CAD7FD4 1456E781
Max Blunt Weapons 3CAD7FD5 1456E781
Max Staff Weapons 3CAD7FD2 1456E781
Max Bow Weapons 3CAD7FD3 1456E781
Max Heavy Arms 3CAD7FD8 1456E781
Max Parry 3CAD7FD9 1456E781
Max Counter Attack 3CAD7FD6 1456E781
Max Dodge 3CAD7FD7 1456E781
Max Double Attack 3CAD7FDD 1456E781
Max Push 3CAD7FDA 1456E781
Max Heal 3CAD7FEC 1456E781
Max Dark 3CAD7FED 1456E781
Max Holy 3CAD7FEB 1456E781
Max Fire 3CAD7FF0 1456E781
Max Magic Resist 3CAD7FEF 1456E781