Here’s something fun for everyone to do, create your own skull that you can use in campaign and firefight.
I’ll start:
Zealot: There’s only elites and no other enemies.
Medic: You have increased health.
SWAT: You can only headshot enemies.
(They also need to bring bandana back. And make skulls findable again.)
Cloak: all enemies have Active Camo. Grunts and Jackals have poor Camo, Elites/Prometheans, etc. have good Camo. If the flood are in the game, they all have poor Camo.
Janitor: All Marines look like Frank and attack with Gravity Mops. -____-
Hordes: Enemy count duplicated.
Bring Assassin back.
And I agree with OP, I want to find skulls.
I’ve a good one. Since IWHBYD has been useless since reach in that i never hear anyone say anything out of the usual maybe it should make the covies and *brometheans tiny.
*yes i’m bringing that back
Dialect Skull - Makes enemies speak Alien or English (Whatever the default is - it reverses it).
Old School Skull: turns the environment into Halo: CE graphics
Wuv Woo: A skull found in Halo Wars that turns scarab beams into rainbows. Bring this back!
Pyrotechnic: Turns on helmet flames.
Reclaimer: Allows the user to call on sentinel aid in battle.
> Old School Skull: turns the environment into Halo: CE graphics
I think everyone can agree, that is the best idea in halo history. Though maybe call it “flashback” to shorten the name. 
Dump Skull: Every time you reload the leftover ammo in the clip is lost.
> Old School Skull: turns the environment into Halo: CE graphics
that’d be pretty sick
Yeah, we need skulls find able again. I really want the Scarab rainbow skull back. Also I guess a skull that turns all enemies Giant.
> Here’s something fun for everyone to do, create your own skull that you can use in campaign and firefight.
>
> I’ll start:
>
> Zealot: There’s only elites and no other enemies.
>
> Medic: You have increased health.
>
> SWAT: You can only headshot enemies.
>
>
>
> (They also need to bring <mark>bandana</mark> back. <mark>And make skulls findable again.</mark>)
If so that should be the most hardest, most obstacle, almost impossible skull to find and retrieve. 
“Nerf”
All weapon firing sounds and explosion sounds are replaced by 343 members saying things like “Pew pew”, or “Boom!”
Also, sounds like the Spartan Laser charging or the Plasma Grenade before detonation are replaced by 343 members’ voices.
Such as “Waaaaaaaaah” for the Splaser, or “WooooOOOOOO” for the Plasma Grenade.
Aliens stick talk regularly, however.
Look Daddy: A skull from Halo Wars which made the grunt methane tanks pop off every time you kill one.
True Marine: Shields only regenerate to quarter full
LOL ROFL: Weapons and characters make laughing noises instead of default.
Black and white: The game goes Black and White
I also would like to look for sculls again.
This isn’t exactly a new skull, but I’d like Sputnik to return.
It was easily the most helpful skull in Halo 2 for a number of reasons, grenade jumping and launches being one of them. Would help with looking for other skulls and breaking out of map.
The original purpose of skulls (before they got dumbed down in Halo 3) was sheer fun and insane stuff. Physics changing stuff.
Sooooooooooo…
Nullify - anything you pummel temporarily becomes lighter
Screech - nearby detonations have a chance to slow down anything within range
I am simply tired of all this difficulty emphasis. And having the same skull set for 3-4 games. And not having skull hunting for 3 of those games.
Ticranium - Headshots are disabled
Hardcore Bro - Allows co-op partners to spawn in on you, when you would normally have to retreat.
Basically allows teammates to spawn near you when it normally says “Enemies nearby”, or “Too dangerous”.
> The original purpose of skulls (before they got dumbed down in Halo 3) was sheer fun and insane stuff. Physics changing stuff.
>
> Sooooooooooo…
>
> Nullify - anything you pummel temporarily becomes lighter
> Screech - nearby detonations have a chance to slow down anything within range
>
> I am simply tired of all this difficulty emphasis. And having the same skull set for 3-4 games. And not having skull hunting for 3 of those games.
The original grunt birthday should return. Launching bodies into the air (because heads still exploded after dead) with the original grunt birthday and Sputnik was hilarious.
Helpful on legendary as well. Shooting dead bodies to cause collateral damage. Loved the physics changes sputnik caused.
> Janitor: All Marines look like Frank and attack with Gravity Mops. -____-
>
> Hordes: Enemy count duplicated.
>
> Bring Assassin back.
>
> And I agree with OP, I want to find skulls.
OMG Janitor for the win XD, honestly though, my biggies are making skulls findable again, working on hidden/secret areas in the missions to put terminals/skulls/awesome Easter eggs in (since halo anniversary skulls and terminals, and halo 4’s terminals are not very hard to find) and adding technique to obtaining the skull (grenade jumping, rocket jumping, using grav lifts etc.). I think in the next Halo, they should make the return of IWHBYD being almost impossible to find, like in Halo 3,where you had to jump through the rings in a specific order, as this was not discovered until months after release.