Waltz

There are so many things they could have done for Halo 3, but sadly that will remain a fantasy.
I would have love to have seen a d-pad command system a.k.a. tell troops to hold, follow, recon, spread, and Halo 2 was mainly based on the multiplayer, but i was disapointed after seeing the E3 trailer/demo and the game turned out nothing like it.
I would have also loved to see map editors, and maybe gun mods, like i remember one of the the producer comments that in certain parts of halo CE. you need this gn or have to decide between two, so it would have been cool to customize your weapon with a scope or suppressor, and maybe the ability to carry an extra gun.
I;m sure one thing i hoped they improved on was grenade throwing, i mean in the first he can throw amazing distance and not grenades can't kill a person and he can barely throw it, he's a cyborg sheesh!