Unlimited Batarangs
At the main options screen press L1 R1 L2 R2, a sound effect confirming the code worked.
Unlock All Weapons and Unlimited Ammo
Begin the Plant Electrocution 2 level. You'll start the Plant Electrocution 2 level first by sliding down near a few holes in the ground. The second hole in the ground will not kill you. Go down into the hole and glide.. You then will see a lit area. Glide down to it andthen pick up a item that you'll find inside.Next, use your grapnel to exit and jump out of the hole. The item you picked up should be the key that is used for the door right beside the vines behind the glass. Go inside the door and fight one of the "Plant Men". You'll then find an envelope that has a "C" on it, in the room. After you complete the game, you can activate this cheat for all weapons and infinite ammunition.