In campaign:
- New music, Halo CE, 2 and 3 used lots of same/similar music and I'm little fed up with them, so ne music please.
- Could be even longer than the Halo campaings so far: +10 proper missions.
- More skulls, and they should be collectable of course.
Firefight: <-- Yeah, it should be in it
- New enemies (of course in campaign too)
- Lots of new weapons and also forerunner and precusor weaponry would be nice, also keep some old weapons (concussion rifle for example)
- New vehicles.
- Vehicle combat based firefight modes and maps.
- Forgeable firefight maps, and also a 'Firefight forgeworld' would be a very nice add. Just imagine, you could create kind of a own campaign in a way.
- Ability to make intial AI spawns and customize invidual AI traits.
Forge:
Lots of new stuff. New pieces to buils from, much more decorative items. Lots of special tools, like in Garry's mod.
Multiplayer:
- More maps on launch, and the map selection should be diverse and have a good competetive based design.
- Gametypes, gametypes and gametypes...
- Deal with the damn quitters.
- A proper skill based ranking system.