I know most of you may not play this but Im going to post this for those of you who want every character that are all max level (level 256)

You need 2 controllers
2 xbox live accounts (gold)
A modded gamertag will count as a gold account

Go into an xbox live game for the campaign
ready up for both your accounts and the other player
Then when ou see the countdown from 4 or 5 seconds wait till it gets to 2 seconds left
Right when it gets to 2 back out of the game
Then go into a local match and then you have every guy all level 256, although 1 or 2 guys may be level 99 or level 10 most likely the skeleton character

Hope this helped