Sign on Zanzibar
On the beach on Zanzibar, you will see signs that say NO SWIMMING. Well, go to your xbox dashboard, go to the Settings, Clock, and change every number you can to 7 , then pop Halo 2 back into your xbox and load it up. WARNING: Do not sign into XBoxLive, it resets your clock. Now go to Split-Screen and start a game on Zanzibar. Go to the beach and look at the sign, it will mention something is missing, and there is a bloody dog's head.

First go to Quarintine Zone. Next look around to your right side and you should see a small tunnel. Walk through it. Now keep on going strait till you see a strip of land that is connected to the wall (There are many strips of land connected to the wall so pick the one that has kind of like a part of a ship or metal hiding it). Walk down the strip of land ( careful not to fall off ) till you reach the end and you should see a floating skull. You must do this on Legendary.

This skull makes things have bigger explosions and more
powerful melee attacks.

When you crash on the level Outskirts step outside and you will see a grunt, kill him. Now look up to you right and left side. You will see two lights. Jump on one and grenade or crouch jump(grenade jump is a little hard on a light)up on the roof. Look around and you will see a small dark pathway. Walk down ithe path and you will find a skull and a couple frags. Pick up the skull and your HUD will disapear. Do this on any difficulty.