Halo: Combat Evolved Anniversary Cheats - Xbox 360

Achievements
Complete each achievement to receive the allotted gamerscore:

343 Guilty Spark (25) - Complete the level "343 Guilty Spark" on any difficulty.
All According to Plan... (10) - Kill all the enemies in the first encounter of "Truth and Reconciliation" without being detected.
Assault on the Control Room (25) - Complete the level "Assault on the Control Room" on any difficulty.
Beachhead (10) - Storm the beach of "The Silent Cartographer" with no marine casualties on Heroic or Legendary.
Believe in a Hero (20) - Complete every level of the game on Heroic difficulty.
Birth of a Spartan (10) - Complete every level of the game on Normal difficulty.
Breaking Quarantine (25) - Escape the Forerunner facility on the level "343 Guilty Spark" in 21 minutes or less.
Bro Hammer (50) - Complete any level on Legendary difficulty cooperatively.
Brovershield (20) - Complete any level on Heroic difficulty cooperatively.
Close Quarters Combat (25) - Complete the level "Truth and Reconciliation" with at least four rounds left in your Sniper Rifle.
Dear Diary... (50) - Read all of the terminals hidden throughout the campaign.
Grenadier (25) - Escape the map room in "The Silent Cartographer" without firing a shot on Heroic or Legendary.
Halo (25) - Complete the level "Halo" on any difficulty.
He's Unstoppable! (20) - Complete any level on Heroic difficulty or higher without taking health damage.
Headhunter (50) - Locate all the skulls hidden throughout the campaign.
Heavy Reading (25) - Read half the terminals hidden throughout the campaign.
How Pedestrian (25) - Complete the level "Halo" on any difficulty without entering a vehicle.
I'll Be Taking That! (25) - Pilot a Banshee on the level "Assault on the Control Room."
Keyes (25) - Complete the level "Keyes" on any difficulty.
Leave It Where It Lay (25) - Complete the level "Two Betrayals" on Legendary difficulty without picking up a new weapon.
Living Legend (50) - Complete every level of the game on Legendary difficulty.
Look Out for the Little Guys (10) - Complete the level "Two Betrayals" on Heroic difficulty or higher without killing any Grunts.
Looks like the Oddball (10) - Find your first campaign skull.
Never Tell Me the Odds (25) - Escape "The Maw" on Legendary with at least a minute left on the count down.
No-Fly Zone (10) - Destroy three of the four Banshees on "Halo" on any difficulty during a single play-through.
Overshields are for Sissies (10) - Complete the level "Pillar of Autumn" on Legendary without picking up an Overshield.
Pillar of Autumn (25) - Complete the level "Pillar of Autumn" on any difficulty.
Popcorn.gif (25) - Kill 100 Flood Infection Forms on the level "Keyes" on Heroic difficulty or above.
Skulls Taken! (25) - Locate half of the skulls hidden throughout the campaign.
Speed Reader (25) - Complete the level "The Library" on Legendary difficulty in 30 minutes or less.
Standard Operating Brocedure (10) - Complete any level on Normal difficulty cooperatively.
That Just Happened (10) - Complete the level "The Library" on Heroic difficulty or higher without dying.
The Library (25) - Complete the level "The Library" on any difficulty.
The Maw (25) - Complete the level "The Maw" on any difficulty.
The Silent Cartographer (25) - Complete the level "The Silent Cartographer" on any difficulty.
This One's for Jenkins! (10) - Kill 50 Flood Combat Forms on the level "343 Guilty Spark" on Heroic difficulty or higher.
This Side Up (10) - Complete the Warthog ride on the level "The Maw" without being forcibly ejected from your vehicle.
Truth and Reconciliation (25) - Complete the level "Truth and Reconciliation" on any difficulty.
Tsantsa (50) - Complete any level with at least three skulls active on Heroic difficulty or higher.
Two Betrayals (25) - Complete the level "Two Betrayals" on any difficulty.
Tying Up Loose Ends (10) - Kill every Elite on the level "Keyes" on Heroic difficulty or above.
Walk it Off (25) - Complete the level "Pillar of Autumn" on Legendary without picking up a health kit.
What have we here? (10) - Read a terminal.
Wraith Hunter (10) - Destroy four Wraith tanks in "Assault on the Control Room" with the Scorpion tank, in a single play.

Unlock Skulls
Bandanna skull - Play the "The Silent Cartographer" level. After the Covenant lock the doors, go to the security override building. Turn right in the tunnel before activating the console, then go outside. Turn right again and to find the exterior of the tunnel you just came through. The skull is on top of this tunnel, at the far end. Grenade jump on top to collect it. This skull which gives you unlimited ammunition.
Boom skull - Play the "Halo" level. Approach the tunnel in a Warthog. Drive to the left, get out, and walk up the narrow path to reach the skull.
Famine skull - Play the "The Silent Cartographer" level. Turn around at the start and walk around the island until you reach the large rock where the Pelican crash site is found later. Walk up the rock to the top to collect the skull.
Foreigner skull - Play the "Truth And Reconciliation" level and enter the large hanger before the brig on the lower level. You will see the Covenant drop ship that Keys eventually pilots. Look inside the door farthest from where you first enter the room and to the right to find the skull. Note: The door is locked and only allows enemies to enter the fight. Run into door when it is opening to enter it.
Iron skull - Play the "The Pillar of Autumn" level. At the start of the level, immediately turn around and look behind the two large boxes by the wall.
Malfunction skull - Play the "Assault On The Control Room" level. Reach the large underground section past the frozen lake with the two Wraiths and the Banshee. Notice the turret on a broken bridge to the right. Walk toward the bridge and look down in the chasm to the left to find a conduit with the skull.
Mythic skull - Play the "Halo" level. At the start, move toward the large waterfall. The skull is behind the large rock with plants growing down above it.
Recession Skull - Play the "343 Guilty Spark" level. After getting off Pelican E419 at the start, turn left to face the left side of a very large glowing green tree. Remain in that direction and move directly ahead while avoiding obstacles. You will eventually reach a hill with two trees and a bush in the middle. The skull can be found behind the bush.