All weapons:

During play, press L1, R2, R2, L1, R1, L2, L1, R2, L2, R2.

GameShark Codes

(M) Must Be On
EC8857B41456E60A 

Infinite Health
4C298C4E145625C5 

Infinite Level Up Points
3CD4ADB41456E79F 

Infinite Magic
801b51380200 

Infinite Keys (On Pickup)
d01b51940001
801b5194270f 

Infinite Orbs (On Pickup)
d01b51980001
801b5198270f 

Infinite Gems (On Pickup)
d01b519c0001
801b519c270f 

Have Fully Powered Up Crossbow
801b50740004 

Have Fully Powered Up Fire Storm
801b505c0004 

Thanks to Revolution readers Not Sal and Aaron the gnome!