1. Forerunner Vehicles! (very surprised no one has mentioned this)
2. Arbiter storyline continued (more explanation on the current status of each of the convenant species, who's working with who)
4. Flood Return (perhaps a different type of flood we haven't encountered before)
5. Brutes (where did they go, explanation and possible incorporation)
6. More original weapons (no rehashes like 4)
7. Duel Wielding (what's Chief doing with his other hand when he's shooting a pistol? haha)
8. Larger Multiplayer Games (16vs16 or 32vs32. It is War Games after all... make it a War!)
9. Chief teaming up with Spartans more in campaign (like reach but hopefully some older familiar faces)
10. Matchmaking support for Custom Games (voted on by the community every week)
11. The ability to play only specified Maps in Multiplayer. (You should be able to pick the map you want to play right from the start. When I'm having a good run on a map, I want to play that exact type of match and level again without having to chance or risk a veto)
12. Bring Firefight Back (V3.0)
13. WAYYY more Interactive Levels and Maps (Let's get some rain, thunder, lightning, let get walls exploding when you shoot them with a rocket launcher or turret). Grenades should cause more destruction. When banshees or Covenant carriers fall from the sky, it should have a impact on it's surroundings. I want to be able to walk in a river and feel the current of the water pushing me, tree's sway from the breeze ect. I want to feel the environment instead of just playing in it 343i
14. Hand to Hand Combat would be an awesome new spin to the dynamics of Halo and offer something fresh to the community. (Let's see how badass a Spartan is without any weapons)
15. Lastly Music needs to be more Combat driven. Halo 4's soundtrack was geared more towards setting the mood. Marty's original scores incorporated many heart pounding tracks with drums.
Halo 5 needs to do what Halo 2 did for Halo. Change the way the player interacts with the environment.
Thank you for reading