In the latest Halo Bulletin, Halo Waypoint details all of the available skulls in the Master Chief collection, what games they are present in and what skulls are active for the LASO playlists for each campaign.  All 37 skulls are divided up into two categories: Scoring (gold) and Non-scoring (silver) skulls.  Scoring skulls add a difficulty multiplier to game scoring and makes things more challenging for players, while non-scoring or zero multiplier skulls either have a neutral effect or help the player.  Zero multiplier skulls disable achievements and leaderboard scoring and times.  All skulls are unlocked with the exception of the pre-order skulls which globally unlock December 12th.  Here is the full list of skulls:

• Anger – Enemies fire their weapons faster and more frequently.
  • Halo 2: Anniversary
• Assassins – All enemies in the game are permanently cloaked.
  • Halo 2: Anniversary
• Bandanna* – Infinite Ammo.
  • Halo CE: Anniversary, Halo 2: Anniversary
• Black Eye – Your shields only recharge when you melee enemies. Bash your way to better health!
  • Halo CE: Anniversary, Halo 2: Anniversary, Halo 3, Halo 4
• Blind – HUD and weapon do not display onscreen.
  • Halo 2 Anniversary, Halo 3, Halo 4
• Bonded Pair* – Co-op skull: When one player dies, the other player gets a large damage boost that lasts a while.
  • Halo 2: Anniversary
• Boom* – Explosions have twice the damage radius. Light fuse, run away.
  • Halo CE: Anniversary, Halo 2: Anniversary
• Catch – Enemies throw and drop more grenades.
  • Halo 2: Anniversary, Halo 3, Halo 4
• Cowbell – Acceleration from explosions is increased.
  • Halo 3, Halo 4
• Envy – Chief trades his flashlight for Active Camo.
  • Halo 2: Anniversary
• Eye Patch – Auto aim features disabled for all weapons. You’ll miss it when it’s gone.
  • Halo CE: Anniversary, Halo 2: Anniversary
• Famine – Weapons dropped by AI have half the ammo they normally would. You might want to pack an extra magazine.
  • Halo CE: Anniversary, Halo 2: Anniversary, Halo 3, Halo 4
• Feather* – Player and enemy melee strikes impart more movement physics.
  • Halo 2: Anniversary
• Fog – The motion tracker is disabled. You’ll miss those eyes in the back of your head.
  • Halo CE: Anniversary, Halo 2: Anniversary, Halo 3, Halo 4
• Foreign – Covenant weapons: How do they work? Players cannot pick up or use Covenant weapons.
  • Halo CE: Anniversary
• Ghost – AI no longer flinch from attacks.
  • Halo 2: Anniversary
• Grunt Birthday Party – Grunt headshots lead to glorious celebrations.
  • Halo CE: Anniversary, Halo 2: Anniversary, Halo 3, Halo 4
• Grunt Funeral* – Grunts die in a blaze of glory. And plasma.
  • Halo CE: Anniversary, Halo 2: Anniversary
• Iron – Death carries a heavy price. Dying in co-op resets you at your last saved checkpoint. Dying solo restarts the level.
  • Halo CE: Anniversary, Halo 2: Anniversary, Halo 3, Halo 4
• IWHBYD – Rare combat dialogue becomes more common.
  • Halo 2: Anniversary, Halo 3, Halo 4
• Jacked – Players can only enter ground vehicles by boarding.
  • Halo 2: Anniversary
• Malfunction – Every time you respawn, a random element of your HUD is disabled.
  • Halo CE: Anniversary, Halo 2: Anniversary
• Masterblaster –  Co-op skull: One player’s shields recharge to overshield level and can only melee while the second player has no shields but infinite ammo. Roles switch after a number of enemy kills.
  • Halo 2: Anniversary
• Mythic – Enemies have increased health.
  • Halo CE: Anniversary, Halo 2: Anniversary, Halo 3, Halo 4
• Piñata* – Punching enemies makes them drop grenades. Beat them ’til candy comes out!
  • Halo CE: Anniversary, Halo 2: Anniversary
• Prophet Birthday Party – Punch that Prophet up to 11.
  • Halo 2: Anniversary
• Recession – Every shot is worth twice the ammo. Save those bullets, playa.
  • Halo CE: Anniversary, Halo 2: Anniversary
• Scarab – All player-held weapons fire Scarab Gun beams.
  • Halo 2: Anniversary
• SO…ANGRY… – Enraged Brutes explode like a frag grenade if not dispatched within seconds. Base Brute score values are increased.
  • Halo 2: Anniversary
• Sputnik – Mass of objects is decreased, making them more easily displaced.
  • Halo 2: Anniversary
• Streaking – Player shields constantly decay at a slow pace but recharge some with every enemy kill.
  • Halo 2: Anniversary
• Swarm – Hunters are much stronger. Base Hunter score values are increased.
  • Halo 2: Anniversary
• That’s Just… Wrong – Increases enemy awareness of player.
  • Halo 2: Anniversary
• They Come Back – Flood Combat Forms spawned by Infection Forms reanimating a corpse are much more dangerous. Flood Combat Form score values are increased.
  • Halo 2: Anniversary
• Thunderstorm – Upgrades the rank of most enemies.
  • Halo 2: Anniversary, Halo 3, Halo 4
• Tilt – Enemy resistances and weaknesses are increased.
  • Halo 3, Halo 4
• Tough Luck – Enemies always go berserk, always dive out of the way, never flee.
  • Halo 3, Halo 4

Here are the skulls active per LASO playlist:

Halo CE: Anniversary

Black Eye, Boom, Fog, Eye Patch, Foreign, Famine, Malfunction, Recession

Halo 2: Anniversary

Anger, Assassins, Black Eye, Blind, Boom, Catch, Fog, Eye Patch, Famine, Iron, Jacked, Malfunction, Masterblaster, Mythic, Recession, SO…ANGRY…, Streaking, That’s Just…Wrong, They Come Back, Thunderstorm

Halo 3

Black Eye, Blind, Catch, Cowbell, Famine, Fog, Grunt Birthday Party, Iron, IWHBYD, Mythic, Thunderstorm, Tilt, Tough Luck

Halo 4

Black Eye, Blind, Catch, Fog, Cowbell, Famine, Iron, Mythic, Thunderstorm, Tilt, Tough Luck