Unlock Batlauncher
At the Title screen, press Circle, Square, Circle, Square, L1, R1, L2, R2.

All Cheats
At the Title screen, press L2, R2, L2, R2, Square, Square, Circle, Circle.

All Power Moves Unlocked
At the Title screen, press L1, L1, R2, R2, L2, R2, L1, R1.

Unlimited Handcuffs
At the Title screen, press Square, Circle, Square, Circle, L2, R2, R2, L2.

Plant Electrocution 2: "All Weapons" and "Unlimited Ammo" cheat
You will start the Plant Electrocution 2 level by sliding down towards some holes in the ground. The second hole is not fatal. Fall into it and glide (to avoid minor damage). You will see a lit area. Glide down there and pick up the item you find inside. Use the grapnel to exit, jump out of the hole, and finish the slide. The item you picked up should be the key do the door right beside the vines behind the glass. Go inside and fight one of the "Plant Men". You will find an envelope that has a "C" on it in the room. When you finish the game, you can activate this cheat for all weapons and unlimited ammunition.

Unlimited Electric Batarangs
Press L1, R1, L2, R2 at the main menu. A sound will confirm correct code entry