I realize the answers to this may differ depending on which platform the game is being played on. I'm interested in the Xbox 360 version myself, but if people know for the other platforms, feel free to answer.
I'm pretty sure online co-op exists, but is there couch co-op where multiple people play on the same system? Is there system link co-op where you can connect with other people on the same network outside of Xbox Live?
Additionally, if there are multiple ways to engage in co-op play, do the types of co-op play available vary depend on which method is utilized? ie. Campaign co-op is only available through xbox live, but you can run around with a friend blowing stuff up in couch co-op.
Best Answer
There is no offline/couch co-op. Online co-op and system link co-op exists for 2 players with both having the same functionality.
The whole campaign and everything else in the game is playable in co-op mode, with drop in/drop out possibility.
You're required to use an online pass code on your account to activate co-op mode on either the PS3 or Xbox 360.