This is just pure conspiracy at this point, and I am sure it is obvious certain things will return (warthogs, AR, ghosts, etc) but I'm going to go ahead and list all the things we've gotten to use in our fine years of Halo so that we may discuss what may and may not return in Halo 4.
Oh God, how did I miss the elephant? I guess because it was nigh-useless in almost any regard. My most favorite thing to do in Halo 3 (besides the insanely fun custom games that seem to not exist so much in Reach) was to get with a buddy and do our best to flip the elephant over to get the "Hold RB to flip... Wait, what? How did you do that?" message.
What is life's greatest illusion? Innocence, my brother.