Below is a list of the Skulls available in Halo: Combat Evolved Anniversary, with instructions on how to get them:
This skull causes death in co-op to reset you to your last checkpoint, and death in solo mode to restart the level - it effectively adds a new level of difficulty.
To get it, on the Pillar of Autumn level, having left cryo storage, go to the back of the room. You can find the skull behind a pyrid of purple containers.
This skull gives all covenant double heatlh, and all sentinels additional shielding.
You can locate it after crashing on Halo. Go to the waterfall in the distance and you will find the skull to the right of it on the ground.
The Foreign Skull means that you can no longer collect Covenant weapons to use in your arsenal.
On Truth and Reconciliation, in the hangar bay, once the third pair of hunters come into the room, you will find the skull behind the door they use - the door will close if you take too long to get it and you will have missed your chance.
This skull means that all shots fired use twice the ammunition.
On 343 Guilty Spark, you will find the Recession Skull to the left of the Facility behind a turret with a drop down behind it. The skull is at the bottom of the drop.
Black Eye Skull:
This is one of the most challenging skulls, meaning that your shields do not recharge unless you melee enemies!
The level you can find this skull on is The Library, and it is located on the first floor near the start of the level. Watch for openings in the roof that the Flood enter through. You need to grenade jump into the one just before the door to the round and yellow room.
The Fog Skull disables the motion tracker.
On the Assault on the Control Room level, find this after moving over the first bridge and descending to the lower floor, the skull is on a platform in the middle of the room - you will need a grenade jump to access it.
This reduces the ammunition dropped by enemies by 50 percent.
On Silent Cartographer, after leaving the Pelican, turn around and head in the other direction. You will come to a plateau on the beach with a ramp up the side. The skull is at the top.
This skull makes explosions twice as effective - in terms of their range of damage.
On Halo, once the Warthog has been dropped off, you will find the skull just before entering the tunnel underground - head to the right and you should see it.
The Bandana skull gives infinite ammo.
On Silent Cartographer having entered the security building and gone down into the tunnel towards the control console, you will need to go into the room and grenade jump up onto the top of the structure.
Grunt Birthday Party Skull:
This is a classic, making every grunt headshot end in a spray of confetti and children's cheering.
On The Maw level, find the skull on a railing near when Foehammer gets shot down.
This skull makes it so that melee attacking an enemy causes them to drop grenades.
On the Two Betrayals level, find the skull on the ledge above the exit of the underground tunnel. You can use a banshee to get it.
Eye Patch Skull:
This skull disables autoaim.
On The Library level, find the skull by looking behind the Index instead of getting it immediately.
The Malfunction skull disables a random part of your HUD each time you respawn.
On Assault on the Control Room, find the skull on one of the pipes coming out of the gorge in the large room having been through the tunnel.
Grunt Funeral Skull:
This causes Grunts to detonate like Plasma grenades. Requires a pre-order code.
Added by: MongooseGeneral Nov 20th 2011, ID#7990