Secrets

Catch Skull
Effect: all enemies have 2 grenades, throw more grenades

Level: The Storm

Location: From the start, go through until you go outside again. When you go outside look straight across there is a small round building straight out there, the skull is on top. In order to get up there you can either use a warthog as a platform or grenade-jump. DO NOT destroy the wraith near the door or the skull will disappear.

Grunt Birthday Party skull
Effect: Headshots on grunts cause heads to explode with confetti.

Where to find: Crow's Nest

How to find: Right after the first objective, while en route to the barracks, you will fall down onto a pipe. At the end of this pipe, look over the edge to see a small space a few feet below you. You must simply drop over and as quicly as you can, pull back to land under the floor you were just on. After that, the skull will be at the end.

Blind Skull
Description: "Shoot from the hip"

Stage: First Stage

How To Find: When you get to the area where you see the Phantom overhead (one of the marines will point it out) jump over the rocks and keep following the path on the right. When you get to the cliff there will be a rock over of the side. The skull is on the end of the rock.

Note: This skull has to be Activated before you start a Campaign map.

Black-Eye Skull
Effect: Melee hits instantly recharges your shield.

Where to find: Crow's Nest

How to find: As soon as you start the level, head straight up to the higher level. Head toward the door with the red light, then turn around. Jump onto the racks, onto the red metal light holders, then onto the ventilation tube. The skull will spawn at the end.

Iron Skull
Effect: When either player dies in Co-Op on any difficulty both players will restart at last check point or in single player if you die you restart the level.

Where to Find: Sierra 117

How to find: In the area where you rescue Sarge, behind the prison cell is a large ledge. Got to the far right side and jump on the boxes, then onto the pipes to get up on the ledge, goto the far end of the ledge, turning two corners the skull is at the far end.

Tough Luck Skull
Effect: Enemies do saving throws

Where to find: Tsavo Highway

On Tsavo Highway, about halfway through the mission (right after you are forced to walk through a large blue barrier), you will come out of a tunnel on the highway, and see a large pipeline on your left. Drop down in between the two, and run to the wall in front of you. Follow the wall all the way to where it connects with the cliff on your right, and turn to the left. There should be a few ledges--simply crouch jump from ledge to ledge, and the last one should have the "Tough Luck" skull on it.

Mythic Skull
Effect: Every enemy on the field now has double their normal amount of health.

Where to find: Halo

How to find: As soon as the mission starts walk up the hill in front of you and into the cave. Hug the right side of the cave and after a large boulder you will see a path on your right, just take the short path and it will be at the end.

Cowbell Skull
Effect: Explosive force increased (sputnik from H2)

Level: The Ark

Location: First pick up a grav lift from the small building near where you fight the scarab. Now proceed through the level until you reach the second sloping hallway (stairway), you should see some partitioned risers (platforms) halfway down. The skull is on the top level. Toss the grav-lift on the right side of the hall so it lands on the fourth little green dot from the door. Then run, jump, and use the grav-lift to propel you to the top. You should reach a ckeckpoint just as you enter the room so it you miss just try again.

Thunderstorm Skull
Mission: The Covenant

Effect: "Field promotions for everyone!" -- Upgrades enemies to their stronger versions.

After you shut down tower 1 and get access to the hornet, fly to tower 2 (the one the arbiter shut down). While walking up the stairs, go to the middle part that connects both and there should be a stair leading up to a platform where the skull is.

The 7 Terminals
The Ark:

1. Start the mission and once you enter the first building take a left into another door and now you should be in a curved corridor. On the inside is a Terminal.
2. After activating the bridge to let your comrades accross the gap, do a 180 and you should see it. (it does not open until you activate the bridge)
3. In the third building after defeating the scarab, kill the group of sleeping covenant, then follow the corridor downwards. Once you reach a door in front that is locked, immediately on the left there's an open door. Go through and walk straight off, then do a 180 to find a secret room. It is in there.

The Covenant:

1. When in the first tower standing on the lift, face the access panel and turn left. Jump over and it's right there.
2. Land your hornet on the second tower, walk towards the entrance but when you see the locked door, do a 180. Should be right in front of you.
3. When in the third tower standing on the lift, face the access panel and turn right. Jump over and it's right there.

Halo:

1. After reaching the end of the first cave, hug the right wall and you will see a building. Jump up onto the walkway and hang a left once inside. It's right there.

IWHBYD Skull
Mission: The Covenant

Effect: "But the dog beat me over the fence" - Unlocks bonus dialogue throughout the game. For most, this is the last skull, so this gives you the Hayabusa Helmet as well.

To get this, get to the room where you "fight" the Prophet of Truth. Let the Arbiter kill him, turn around, and kill all the Flood here as well; makes it a LOT easier. With all obstacles out of the way, you need to jump through the Halo holograms here in a specific order, listed below:

4 6 5 4 5 3 4

When you jump through the final hologram, they all light up in a sequential pattern. The Skull will be at the end waiting for you right before the energy bridge leading to Truth's corpse.

Fog Skull
Mission: Floodgate

Effect: "You’ll miss those eyes in the back of your head." -- Your motion sensor disappears.

As you are walking down from the anti-air gun you destroyed in the previous mission, you encounter a ramp (next to a missile launcher). Around this ramp, you hit a checkpoint. At this point, you should also hear a marine yelling, ’There! Over There!’. Look up and to the right, directly at the roof of the building next to the missle launcher. There is a single flood form (not to be mistaken with the two other flood forms jumping in front of you) which is holding the skull. Kill him before he jumps, and he will drop the skull down to the ground where you can retrieve it. Too early, and the skull will get stuck on the roof though, so just time it carefully.

Famine Skull
Mission: The Ark

Effect: "Trust us. Bring a magazine." -- Dropped weapons will have very little ammo compared to normal.

When you first go into the valley to the right after the wrecked phantom, look to your left where you will see a huge boulder. Use a ghost and get to the side of the boulder that is closest to the bridge overhead. It is easy to pilot the ghost up the side of the wall using the thrust. To get the skull, pilot 2 ghosts up the wall to the top of the bridge and stack them one on top of another next to the beam where the skull is placed. Simply jump from the top of the ghosts towards the skull and land on the beam.

Tilt Skull
Mission: Cortana

Effect: "What was once resistant is now immunity" -- Enemies have different body parts that may be resistance to certain bullet types

When in the circular type room with all the flood look for a small structure piece next to two archways, jump on top if it and up on the rocks to the top left, turn left and jump up again, then do a 180 and jump to the rocks across from you. After that follow the the rock sticking out and leading up on top of of the original circular room, the skull will be in a pile of blood.

Unlockables

Achievements
Complete each achievement to get the allotted gamerscore.

Armor Permutations Unlockables
Body Pieces: Spartan marked with (S) and Elite marked with (E).

Multiplayer Ranks
A list of the Skill and Experience needed to advance in rank. Note: you can skip ranks once there is a set skill requirement. For example, many people go from Lieutenant Grade 2 (Skill:10 EXP:85) straight to Captain (Skill:20 EXP:100)

Multiplayer Medals
If you do the following things you will get the medal while playing multiplayer. When you do the task usually it will show you by a little icon of the said medal appearing in the corner of the screen. Also at the end of each match you can check what medals you got. You can also check your overall medal count on bungie's official website. A very small amount of these are secret medals in that they don't tell you right when you get them but they will appear in your medal history. (One example of such a medal is the Steaktacular! Medal)

Codes

Hide Weapon, Show Coordinates & Camera Modes
The following cheats can be performed during a local match or replay only. You must simultaneously PRESS & HOLD the following buttons for 3 SECONDS to toggle the effect on / off.

KEYS:
LB = Left Bumper
RB = Right Bumper
LS = Click in on Left Analog Stick
RS = Click in on Right Alalog Stick