Wow... pretty much what I was gonna say. I guess I'll add to it a bit, then.
-A bit more promethean weapons. Thought the weapons themselves were impressive, but not the amount.
-A UNSC air vehicle. Would prefer the Hornet, but seeing Falcon again wouldn't be too bad, either.
-Water vehicles. Bungie had been planning to do it since CE, but never did. I'm just interested for how this could turn out.
-Invasion. Where did it go?
-I know this has been said enough, but Forge World should return.
-Flood. Sure, their levels turned my friend paranoid for a couple months and they frustrated me, but I would love to fight them at least once more.
-Scarabs. I don't recall seeing a single one in 4. Quite the disappointment. I know this has been said, but driving them would be a great dream come true.
-Pelicans. Ok. A wish was granted in Halo 4. We drove a pelican. Why once? Where is it in multiplayer? I think it could be interesting. Also, if implemented in MP why not take the SpLasers off? Oh... how OP it could be if not... :wallbash:
-Elites. I missed playing as an elite while I was a Reach noob.
-Elephants. Where... is... my... mobile... base!? More than 1 map with them, please?
-More promethean types. I'm almost certain this will happen since the Covenant is constantly evolving. Why about 3 types of enemies?
-Firefight. I played it when I was bored and lonely.
-More ideas because for some strange reason I forgot all mine.
You and me both...