So the skulls for Halo 2 Anniversary have been found out.  This info was passed on to me by HFFL member Rythmic Warrior. There is a LOT more skulls than I had thought there would be.

I have to admit, some of these seem a bit ridiculous. And I can’t imagine have a LASO run with all of these active. That would be beyond cray cray…

Anger Enemies fire weapons much more aggressively. MOAR Bullets!
Assassins All enemies are cloaked. Invisassins!
Bandana Unlimited ammo and grenades. No NOT Banana!
Blind Your HUD disappears and your weapon does not display. You got the Wal*Mart HUD!
Boom All explosion physics impulses are increased. Michael Bay Skull
Black Eye Your shields will only recharge after you melee an enemy. Go all MMA on their Covenant Asses
Catch Enemies throw more grenades. Anyone for stickies?
Envy The Chief has Active Camo and the Arbiter gets a flashlight. This is NOT a measuring contest…
Eye Patch Disables auto-aim. The Nick Fury special
Famine Dropped weapons have significantly less ammo. Cheap thrills.
Feather All melee strikes impart additional force. More like BAMtam weight!
Fog Your motion tracker is disabled. No, not Frog protection…
Foreign You cannot pick up Covenant weapons. Purple is SO heavy!
Ghost Allies and enemies no longer flinch, meaning they shoot more often. They’ll finish the fight, one way or another.
Grunt Birthday Party Grunt head shots release party favors. YEAAAAAH!
Grunt Funeral Grunts explode after death. Methane is dangerous!
Iron Don’t die. Playing solo you have to start the mission over. In co-op you’re all sent back to the last checkpoint.
IWHBYD Rare dialog is more common, and vice versa. Wait, what did they say?
Jacked You can only pilot a vehicle by hijacking it. One time where ‘jacking’ is perfectly ok.
Malfunction Each death removes a random element of your HUD. Who fixed this, a Grunt?
Masterblaster (Co-Op Only) One player has recharging over shields and can only melee. The second player has no shields, but infinite ammo. Roles switch after a random number of kills. Jack Sprat could eat no fat, his wife could eat no lean.
Mythic Enemies have increased health and shields. Power UP!
Piñata Enemies drop a plasma grenade when you hit them with a melee attack. Pooping Plasma
Prophet Birthday Party Every smack to the Prophet of Regret’s face is accompanied by epic Steve Vai guitar licks and lightning bolts. <–Seriously???
Recession Every shot uses two ammo. Two for the price of one!
Scarab All player-held weapons fire the Scarab Gun beam. Unlocked when you find all the original Halo 2 Skulls.
So ... Angry … Enraged Brutes will explode shortly after enraging. You wouldn’t like them when they’re angry.
Sputnik Mass of all objects is reduced. Combine with Boom and Feather for maximum enjoyment.
Straking Your shields constantly decay, but recharge a bit after each enemy kill. BRAINNSSSS
Swarm Let go my golo! Hunters are even more robust and deal extra damage with attacks. Unlocked after you watch all five episodes of Halo: Nightfall on the Halo Channel and complete the associated challenges.
That’s Just … Wrong Enemies have a cyborg-detecting sixth sense.
They Come Back Infection Forms that reanimate a corpse are much stronger than normal. Hey, not fair!!!
Thunderstorm Field promotions for every enemy in the Chief’s path. You get a stripe, he gets a stripe, EVERYBODY gets a stripe!