There are some slight changes I would like to see done to the multiplayer that would really make me happy as someone who plays Halo competitively. First, I hate the fact that you can shoot grenades out of the air and make them explode. Yes, it makes for some funny moments but when your own grenade gets blown up in your hand and kills you, it sucks. I'd like that removed because when it happens, it's complete luck. No player intended for it to happen and I don't think that's cool. Also, bring back insta-spolsion the way it was implemented in Halo 3. It was difficult to do, required skill and was a whole lot of fun. It only happens sometimes now in Reach. Let's make it happen all the time.
I had some more but I forgot them lol