I personally, would like to see some Mantis-based obstacle course/HORSE maps. That would add an extra twist to things instead of obstacle courses for just Spartans.
What do you think and/or want to see involving the Mantis.
Firefight is a classic. You run around like Master CHief killing Covenant and having fun.
Spartan Ops is more like a second campaign. It will be a good change from Reach and Halo 3.
It would be nice to have both though incase you're either bored of firefight or waiting for the next Spartan Ops "episode".
I was watching things on waypoint today and found a video that gives you a good look of Halo 4 and master Chief.
Link: http://blogs.halo.xbox.com/post/2012/10/02/Enjoy-It-A-Halo-4-Video.aspx