Unlimited Batarangs:
At the main options screen, press L1 R1 L2 R2, and you hear a sound confirming the code

All Weapons + Unlimited Ammo:
At the start Plant Electrocution 2 level, slide into the second hole and glide to the lit area and pick up the key. Use the grapnel to exit, continue the slide down and use the key on the door right next to the vines behind the glass. Inside you will find an envelope with a "C" on it. When you win the game, activate the cheat.

Enter the following cheats at the main menu.

ALL CHEATS

Press L2, R2, L2, R2, Square, Square, O, O.

UNLIMITED BATCUFFS

Press Square, O, Square, O, L2, R2, R2, L2.

UNLIMITED BAT LAUNCHER

Press O, Square, O, Square, L1, R1, L2, R2.

UNLIMITED ELECTRIC BATARANGS

Press L1, R1, L2, R2.

All Power Moves Unlocked:
To unlock all power moves, enter the following code at the title screen: L1, L1, R2, R2, L2, R2, L1, R1.

Unlimited Batlauncher:
To unlock the unlimited batlauncher, enter the following code at the main title screen: CIRCLE, SQUARE, CIRCLE, SQUARE, L1, R1, L2, R2.

Unlimited Handcuffs:
To unlock an unlimited supply of handcuffs, enter the following code at the title screen: SQUARE, CIRCLE, SQUARE, CIRCLE, L2, R2, R2, L2.

Unlock All Cheats:
To unlock all of the cheats in the game, enter the following code at the title screen: L2, R2, L2, R2, SQUARE, SQUARE, CIRCLE, CIRCLE.

To have 99 of each item, go to the main menu and enter this code: L, R, Y, Y.

To play as an invincible Batman, go to the main menu and enter this code: L, R, X, L, R, Y, L.

press l2 r2 square circle triangle circle r1 l1 and batman will be wearing the costume from the origional batman show(the one starring adam west)

To unlock everything, go to the main menu and enter this code: L, R, L, R, X, X.