map terrain editor, bots and MOAR violence (the game is already mature so it doesnt matter)
map terrain editor: yeah ! I want to be able to decide if I want sand or grass, if I want to just make holes or mountains off the terrain, kinda like the farcry map editor.
bots in multiplayer, not firefight or anything, spartan bots, that you can switch their difficulty and they give medals when you kill them, should be ONLY for custom games.
more violence: hell yeah, a sword lunge should slice a spartan in half, rocket should literally explode a spartan, sniper bullets should make holes on the armor, any damage at all should do permanent damage on the armor (well until he die)
last thing that I wanted recently and im sure you guys tought about it, its the end game kill cam... please... that would be awesome