Skulls

There are an unknown number of Skulls created by General and it is unknown all of their effects. But their power has been felt all across the land. 
== Halo 2 Skulls ==
* Whuppopotamus (That's Just... Wrong...)
** AI become more observant, noticing even active camouflage, shadows, the sound of reloading or drawing a weapon, footsteps, etc. They also have better accuracy and are much less likely to kill themselves or their teammates with explosive weapons. 
*** POSSIBLE: Increases sound of the user and distorts all incoming weaponry, making you a walking target. 
* Thunderstorm
** Enemies get a boost in rank.
*** POSSIBLE: Makes all enemies their apex selves. 
* Blind
** HUD becomes invisible; you cannot see your weapon, body, shields, ammunition, motion tracker, or use your flashlight. 
*** POSSIBLE: Forced Remote Viewing power, but you're still in your own body. 
* I Would Have Been Your Daddy
** Rare combat dialogue becomes more common; and vice versa. 
*** POSSIBLE: Like alcohol, it lowers the inhibitions of everyone around you - you might hear weird shit. 
* Catch
** AI will throw more grenades and drop two grenades when killed. 
*** POSSIBLE: INFINITE GRENADES!!!!1!
* Grunt Birthday Party (Mindblown)
** Headshots on any race turn into Plasma Grenade explosions. 
*** POSSIBLE: Also known as the Mindblown Skull, when the head explodes from a headshot, the resulting force is equal to a grenade explosion.
* Famine
** All dropped weapons have half ammo, but not weapons generated at a static point in game. 
*** POSSIBLE: All weapons around the user become empty, inexplicably.
* Envy
** Master Chief trades his flashlight for the Arbiter's active camouflage. 
*** POSSIBLE: Trades abilities for nearby people, as if you were them for a time. Including knitting. 
* Assassins
** All enemies are permanently camouflaged. 
*** POSSIBLE: All living things are disguised from your sight. 
* Mythic
** All enemies and allies have double the health and shielding they have on Legendary. 
*** POSSIBLE: Coverage under the Covenant Health Plan. 
* Sputnik
** The mass of certain objects is severely reduced, making them fly further when smacked with a melee hit or when they are near an explosion. Enemies also spin around when you hit them, allowing you to kill them in two hits. 
*** POSSIBLE: Mass is reduced in all objects around you... 
* Angry
** Enemies fire their weapons faster and more frequently. 
*** POSSIBLE: Turns you into the thing everybody hates most and lowers their control - they will go nuts over each other to kill you. 
* Ghost
** AI characters do not flinch from attacks
*** POSSIBLE: Nobody has any fear any more... be prepared for awkward conversations. 
* Iron
** When playing co-op, if either player dies, the game restarts both of you to your last checkpoint.
*** POSSIBLE: Death actually means PERMA-DEATH. Careful... this Skull is Hungry...
* Black Eye
** Shields do not recharge automatically, only recharging when you kill ANYTHING with a melee attack (minus the energy sword)
*** POSSIBLE: The Skull will permanently suck away your health - the only way to get it back is to harm others. You can gain godlike powers if you continue to harm others.
== Halo 3 Skulls ==
=== Gold Skulls ===
* Iron
** If a solo player dies, the level is restarted. If a co-op player dies, the last checkpoint is loaded. 
* Black Eye
** Shields only regenerate by melee attacking enemies. 
* Tough Luck
** Grenades, projectiles, and vehicles are evaded more effectively by the AI. Brutes will berserk more often and Grunts will kamikaze more frequently. 
* Catch
** All AI units throw many grenades; dropping more.
* Fog
** The motion sensor is disabled.
*** POSSIBLE: It's like being high, drunk, and sexually satisfied all at once.... apathy abounds!
* Famine
** Dropped weapons have much less ammunition/charge.
* Thunderstorm
** PROMOTIONS ALL AROUND!!
* Tilt
** Enemy defensive resistances and their weakpoints are doubled.
*** POSSIBLE: What was strong - is now impenetrable. What was weak - is now an instakill!
* Mythic
** All Covenant Enemies have twice as much health
=== Silver Skulls ===
* Blind
** See above
* Grunt Birthday Party
** Grunts explode in confetti, applause, and children's laughter when headshot
*** POSSIBLE: Happiness ensues...
* Cowbell
** All explosions are amplified. (See Sputnik)
* IWHBYD
** See above. 
* Ultimate Blind Skull
** Same as the regular Blind Skull, but if carried through to the next mission, you start with a Spartan Laser instead of an MA5C
*** POSSIBLE: If you deal with this Blind Skull for long enough, you will gain a Scarab Laser upgrade to your weapons. 
=== Mythic Skulls ===
* Orbital Skull
** Marked with the Space Elevator
*** POSSIBLE: Allows you to walk in space without fear of reentry or gravity... or mass. Also... scary as shit on the ground. 
* Assembly Skull
** Marked with a Lekgolo
*** POSSIBLE: Separates you into a colony of Lekgolo... Pull yourself together man.
* Sandbox Skull
** Marked with the Monitor
*** POSSIBLE: It's like Forge, but in real life. Nothing like a scorpion appearing out of thin air and spinning impossibly, merged horrifically with a Mantis and some fusion coils. 
* Heretic Skull
** Marked with the Mark of Shame
*** POSSIBLE: Unknown purpose, but somehow related to the Pious Inquisitor. 
* Longshore Skull
** Marked with a harpooned fish
*** POSSIBLE: Unknown purpose, but somehow related to Old Mombasa's quays.
* Citadel Skull
** Marked with the Covenant Citadel
*** POSSIBLE: Unknown purpose, but somehow related to the Forerunner Ruins on the surface of a desert planet. 
== Halo Wars Skulls ==
* Look Daddy!
** When Grunts die, their methane tanks always shoot off, causing more damage to nearby forces. 
* Grunt Birthday Party
** When Grunts die, they explode into confetti.
* Cowbell
** Destruction physics magnified. 
* Wuv Woo
** Scarabs shoot a rainbow made of pure love and hearts. 
* Fog
** No minimap
* Sickness
** All player units have 50% few hit points
* Rebel Sympathizer
** Nonplayer units get 25% more hit points. 
* Rebel Supporter
** Nonplayer units do 50% more damage. 
* Rebel Leader
** Nonplayer units all start with extra veterancy
* Catch
** All player units' abilities recharge in half the time
* Sugar Cookies
** All player units have 50% more hitpoints
* Boomstick
** A 5% chance that any nonplayer unit detonates upon death
* Pain Train
** All player units train 50% faster.
* Bountiful Harvest
** Supplies come in 25% faster
* Emperor
** All player powers recharge in half the time
== Halo Reach Skulls ==
* Cloud
** See Fog
* Custom Skulls
** Allows players to define traits such as enemy firing style, luck, and player traits (max of 3)
== Halo: Combat Evolved Anniversary Skulls ==
* Iron
** Iron.
* Mythic
** Covenant gain double health, Sentinels energy shields. 
* Boom
** Explosion radius will increase x2
* Foreign
** Covenant weapons are unusable
* Famine
** Famine.
* Bandanna
** Supplies infinite ammo and grenades. 
* Fog
** Fog/Cloud. 
* Malfunction
** Every respawn, a new element of the HUD will disappear. 
* Recession
** Every shot is worth twice the ammo. 
* Black Eye
** Black Eye
* Eye Patch
** Auto Aim is disabled for all weapons
* Pinata
** Punching enemies will make grenades drop
* Grunt Birthday Party
** Confetti, cheering, laughter, etc. 
* Grunt Funeral
** Grunt's methane tanks explode upon death
== Halo 4 Skulls ==
* Famine
** Famine
* Tilt
** Tilt
* Mythic
** Coverage under the Covenant Health Plan
* Catch
** Catch
* Black Eye
** Black Eye
* Tough Luck
** Enemies always go berserk, always evade, never flee. 
* Iron
** Iron...
* Thunderstorm
** PROMOTIONS ALL AROUND
* Cowbell
** Sputnik
* IWHBYD
** BADBMOTF
* Grunt Birthday Party
** GBP
* Blind
** Blind
== Halo: Spartan Assault / Spartan Strike Skulls ==
* Hollow
** No health, only shield. 
* Pacifist
** Shields and armor deplete while firing weapons. 
* Famine
** Famine.
* Black Eye
** Black Eye. 
* Thunderstorm
** Enemies have more health (see Mythic).
* Blind
** Blind.
== Halo 2 Anniversary Skulls ==
* Pinata
** Enemies drop grenades when melee attacked. 
* Bandanna
** Players have infinite ammo and grenades, but need to reload. 
* Grunt Funeral
** Grunt Funeral
* Bonded Pair
** In co-op, when one player dies, the other receives a 100% damage boost for 60 seconds.
* Swarm
** Hunters do double damage and have triple health
* Scarab
** All player weapons become Scarab Guns
* Prophet Birthday Party
** Every smack to the Prophet of Regret's face is accompanied by epic guitar licks and lightning bolts.
* So... Angry...
** Enraged Brutes will explode like frags after berserking. 
* They Come Back
** Combat Forms that are reanimated by Infection Forms are much stronger than normal. 
* Jacked
** Players can only enter vehicles by hijacking.