Get all weapons and max ammo

When you are at the Plant Electrocution Level 2 slide down toward the holes in the ground and enter the 2nd hole. Make sure to glide into the hole and then glide towards the lighted area. Here you pick up the items. Use the grapple to get out and finish your slide. The key you have just picked up is for the door beside the vines behind the glass. Now Enter and defeat the plant man and you'll get an envelope that has a 'C' on it. When you finish the game this will activate the cheats.

All 5 Envelopes

Envelope A - "Rooftop Battle"
Once you grapple to the building with the door you have to jump across to get to, jump off of either of the little ledges onto the roof of the building. Run until you get next to the fence with the rows of trees behind it, then jump off of the closest edge, just below the edge of the building is a small ledge just big enough for Batman to walk on. Follow the ledge around the left side of the building until you see a Grapple Point. Grapple up to the ledge and inside of the door is Envelope A.

Envelope B- "The Bridge"
This Envelope is at the very beginning of the level and you can see that it is located on top of a large box to the left. To get to it climb the ladder. At the top of the ladder is a box that is blocking the way but is slightly facing one side. The trick is to jump off the end of the box without falling off and use the Gliding Cape move to soar around the end of the box and onto the box on the other side. You will have to jump off the box and glide around one more in order to walk all the way around to get the Envelope.

Envelope C- "Plant Electrocution 2"
(See other Hint)

Envelope D- "Gasworks"
This one is easy to get. Just find the area in the Gasworks building that has the green river of toxic waste with the boxes floating in it (theres only one). Just Glide down to the boxes and jump from one to the next until you reach the Envelope.

Envelope E- "Swat Chase"
This one probably the easiest. Get to the very very bottom of the elevator shaft. At the bottom is an electrical box (You can use a remote charge to blow it up). Once it has been destroyed the door will open just above you. Go in the door and get the key which will open up another door that is at the very top of the elevator shaft, inside is the last Envelope.

Cheat Mode

At the Main Menu, press L, R, L, R, X, X, Y, Y.

Unlimited Electric Batarangs

At the Main Menu, press L, R, Y, X.

All Power Moves and 120 Achievement Points

At the Main Menu, press L, L, R, R, L, R, L, R.

Infinite Handcuffs

At the Main Menu, press X, Y, X, Y, L, R, R, L, L.

Infinite Batlauncher

At the Main Menu, press Y, X, Y, X, L, R, L, R.

Blimp Puzzle

Look in your inventory and examine the disc Batman picked up before fighting Mr. Freeze. It will reveal possible colors that work with the Blimp puzzle. The combination is Purple and Green. Make the color purple, "mix tubes", then make the color green.

Bruce in warehouse level disquise

Press L, R(2), L, R(2), L, R, L, R(2), L at the main menu, then hold L while selecting the level.

99 of all items

Press L, R, Y(2) at the main menu. A sound will confirm correct code entry.

Invincibility

Press L, R, X, L, R, Y, L at the main menu. A sound will confirm correct code entry.

Master Code

Press L, R, L, R, X(2) at the main menu. A sound will confirm correct code entry.

Funny bones warehouse lock

Instead of trying the 999 possibilities on the lock, look for figurines like the one in the room near your starting location. There is another one behind trucks and one outside the fence when you get on the roof of the building with the first figurine. The combination is 619 (from left to right).

Unlock All Movies

To unlock (and view) all FMVs in the game, enter this code at the main menu: L, L, X, X, Y, X, L, R.