I know most everyone on here has played Halo and everyone has a favorite. But personally, my favorite (Combat Evolved) isn't my favorite to play co-op on. ODST is my favorite Halo to play cooperatively. And not even because of Firefight mode. I really enjoyed grabbing Mongoose(es?) with some friends and drive around the city at night. Or loading into Warthogs on some of the other missions. It really felt like you had your own ODST Team. Reach probably came in second for similar reasons. So what about everyone else? I didn't include Wars or Spartan Assault for a reason in case anyone was wondering (I don't even remember if they have co-op campaign or not anyways).