I didn't see any stickied threads containing a complete list (or as complete as I tend to see fit), so here goes. Sorry if you don't do this kind of thing here (as Google is the almighty finder of things).

Skulls

Blind - Mission: Sierra 117

The first skull in the game! It's a simple one to find. Once the first Phantom that drops off troops appears, you know you're in the right area. Kill all the enemies, then hug the right wall of map and you'll reach some rocks and the ocean. Jump across the rocks until you find the one with the skull.

Iron - Mission : Sierra 117

Play the level normally until you get to Quid Pro Quo. Snipe down the enemies (not required, but highly suggested on Legendary) and move toward the right of the map (from cliff view) where the bridge is laid out. Continue bashing your way through enemies until the bridge is clear, then head back to the start of the bridge. Look down through a scope and look for platforms on the right side, about a quarter into the bridge. Hop on and keep going on the final ledge you'll get to. It goes for a while. At the end, your skull.

Black Eye - Mission : Crow's Nest

At the very beginning of the level, go up the stairs instead of down into the tunnels. At the top you should see a barrel and this cage-like thing. Jump onto the cage like thing, then jump onto the red railing to your right. From there, jump on the pipe. At the end of the pipe: your skull.

Grunt Birthday Party - Mission : Crow's Nest

When you reach the point in the level where you're inside a giant pipe with drones flying in and out, you're in the spot. Go to the edge of the pipe, then go down then back in, so you land on a seperate, lower level of the pipe. At the very end of the pipe should be the skull (note the skull is inside that level of the pipe, not where you landed).

Tough Luck - Mission : Tsavo Highway

Play the level normally until you reach the point where the recon team informs the commander there are "cruisers above, inbound". Retrace your steps to the pipe on the right (left if coming from the cave, right if retracing steps). Jump onto the building, then on the pipe. Continue until you reach the yellow barricade on the pipe with a regenerator. Jump over that yellow barricade, then look to your left. Your should see this little bolt-looking thing, extending from the pipe. Jump on top of that, then down onto the rocky platform below. Follow that platform to it's end, look to your left, and you see the skull sitting there. Simply jump over to it and it's yours.

Catch - Mission : The Storm

Play the level normally until you reach the giant dirt field with a Wraith on the far corner and the AA Wraith in the middle. Play it out normally, however do not destroy the Wraith. Drive a Warthog next to the giant cylinder in the middle, get on a dirt mound, then get out. Jump on top of the Warthog, then onto the top of the pillar. If you can't, grenade jump off the Warthog. On top is your skull, if you have done it correctly.

Fog - Mission : Floodgate

At the beginning of the level, head out to the normal spot, however upon reaching the sandbags, look up and to your right. There should be a building rooftop. Keep your BR Scope on that spot, and head shot the Flood that comes out. However, time it right, or else the skull will drop on the building or over the fence. If done correctly, simply follow the skull's flight to the ground, and retrieve.

Famine - Mission : The Ark

Play through the level normally until you get to the point where Johnson tells you there's a good spot for an LZ. Follow the Pelican and kill the enemies, but turn back once you get to the cave. Find the rock on the right (if retracing steps) that leads to a giant platform of rock, then leads to a bridge. Drive all the Ghosts possible up there, to the edge of the bridge. Don't try to drive up there, just make a ramp of Ghosts. Then drive a Prowler up there and use the ramp to get on the bridge. Drive the Prowler to the near end of the bridge where it extends on the left side. Position the Prower in a way so you may jump on the turrent end, then onto that ledge. Get onto that ledge and the skull is yours.

Cowbell - Mission : The Ark

Once you've destroyed the Scarab Tank, go inside the building in the middle of the dirt. Inside are Grav Lifts. Take one of 'em and go inside where the game generally tells you to go. Inside the building, once you see a spot where there's a ramp going down and there are different levels on the left hand side, used as an overhead for the floor at one spot. Put the Grav Lift on top of one of the breaks in the wall on the right, then hop on. If done right, you'll land inside that overhead on the level with the skull.

Thunderstorm - Mission : The Covenant

Alright, this one is deep into the level. Once you get to fly a Hornet, you're in the right place. Fly it over to the second tower, the one where the Arbiter and Elites have already gone and disabled. Ignore any messages telling you to ignore the building and land the Hornet on that mid section. At the end, the skull.

IWHBYD - Mission : The Covenant

This one is kinda complex. This skull is as deep into the level as possible. Play normally until the cut-scene where the Arbiter kills the Prophet of Truth. Flush out all the Flood, and locate a ring that has red on it (in the middle). Jump through the ring without touching it. You'll have to jump through others, as well. The ring closest to the 'exit' is 0, the one closest to the Prophet's Death Site, 7. The order for the rings is..

4654534 (The first four is the one I told you to jump through)

If done correctly all the rings will light up and flash. Backtrack to the bridge you extended to reach truth. At the end, your skull.

Tilt - Mission : Cortana

Play normally until you enter a room where Cortana says she likes to play games. Kill all enemies, ignore the spores, and find a purple thing that looks like a drop pod, only the lid is open. It's on the right side from the spot you enter. Jump on it, then onto the lid, then look to your left. Jump onto that ledge, then again onto the ledge above. Watch out for corners. From the one above, jump across, onto that one. Cross the bridge to your right and the skull is in a pile of..blood?

Mythic - Mission : Halo

Last one, you can do it! At the beginning of the level just hug the right wall and keep hugging it into a tunnel. Low and behold, the last skull.

Terminals

There are 8 Terminals in the game, and once you read through all of them (only press B when the red light is prompted at the very very end), you get the Marathon Man achievement.

The Ark - 3 Terminals

These ones are hidden. Ok, first one is in a building right after you defeat the first group of Covenant. Take the door on the left instead of running across the hall. Look on the right side. Hold RB as prompted and mash A (what I did. I got impatient). Keep mashing until you see a red light on the bottom left. Second one is right behind you once you extend the bridge for the vehicles. Third is in the last building you enter. Find the room with the sleeping covenant. Look for another door than the usual one you take. From there there are two different doors, both lead eventually to the room with the terminal.

The Covenant - 3 Terminals

One in each tower. From the elevator, jump to the left, and once the terminal opens it looks like an eye.

Cortana - 1 Terminal

Find the room in which you found the Tilt skull. Drop below the floor (there is room for this normally on the edges). Kill any flood you find and search.

Halo - 1 Terminal

Go forward from the beginning of the level until you see some structural beams. Then turn right, then look for other beams. Once inside the building you find, take a left. Behold, the last terminal.

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Alright, that should be it, unless you guys want armor permutations. If so, I'll post pictures, but it may take a day or two, as I'd have to find the ones I don't have yet.

Thanks for that. Must try and get these now.

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There are two rules in life:
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Rule #2: Always obey rule number 1.

Might have to go back to Halo now. I got the first three skulls then kinda left the game in on the shelf.

Still need to play game on the harder setting also, but I think I'll need some help with that. . Struggled on the level that looks like the inside of an ear, Cortana, I think its called. Had to call on a Big gun to help me get passed it.

Sir Dementia if your still around, Thanks again

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Glad I could help. Also, I forgot the IWHBYD skull. Editted first post to include it.

Thanks for the guide...I got me some skulls

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I would consider playing the campaign mode again in Halo but that would mean I would have to play the penultimate level again. Playing it through once was bad enough but there is no way I could hack another go.

Has there every been a level as badly designed in an otherwise quality game as that?

Nice work though on the guide.

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Cheers for the post! I may have to look for some skulls sometime.

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