-More blood and gore effects (can be disabled for queasy players). I'm talking blood oozing out of freshly killed enemies and bodies being blown apart or peppered by explosions. This is an M rated game already, there's nothing to lose by adding some realism. I know it's too late to add this into Halo 5, but maybe Halo 6?
-Please take out those clips of Spartans posing and high-fiving before and after multiplayer games. It's so cheesy. Are Spartans futuristic super-soldiers or douchey frat bros? Show something heroic and cool like shots of them dropping in from orbit or a pelican or something and then charging into the fight. Do you really think humanity's strongest warriors should act so boyish?
-The automatic call-outs are a good idea, but some of them are annoying. Keep the Spartan voices flat and serious instead of injecting silly personalities into them. It's less distracting to hear "Sniper Rifle Acquired" than "I GOT SNIPES"
-What's the point of shoulder charge if it doesn't do any more damage than a regular melee?
-Prophet's Bane needs to have its ammo count reduced. It's just too oppressive as it is. I feel like whichever team gets it first almost always wins the game. This is just anecdotal though.
-Ground pound is insanely funny to use, but needs a buff to be a viable mechanic. It's too easy to dodge and its range is too limited to be practical. Increase its damage and splash radius, increase its range, increase flight speed, but also increase its charge-up time to prevent abuse as a way to travel or escape, and maybe even have it deal some damage to the player using it. At the moment it's just too underpowered to be useful as anything other than a funny way to try and kill people while drunk with friends. If you try to get kills with ground pound, you will perform much worse in that game than if you didn't.
-The main menu music is not bad by musical standards, but it doesn't sound like Halo. It's got that generic, uninspired, cliche "hero" feel to it that's been used in countless superhero and war movies. Still, it's better than the bizarre main menu theme from Halo 4. I don't even know what to say about that one. Can you guys just pick Marty up? Even for just a couple songs?
-Make the thruster bursts a bit more flashy. Visually speaking they could use some more umph.
-Why are the crosshairs in the DMR's scope a sickly, nauseous yellow? It gets washed out against light sources and clashes with the color scheme of the rest of the human weapons.
-There seems to be a delay between landing a kill shot on an enemy and getting confirmation of that kill. It just doesn't feel right, as if it's not registering as fast as it should on the killfeed and medal tracker. Even the dying animation seems delayed to me. Could just be me though, idk.