I saw this on a webpage a while ago: This glitch will unlock the Foundation map, even if you don't xbox live. If you play the last level in campaign in co-op mode, using one profile which has allready beaten the game, and a fresh one, and in the latter part of the level (when you have the banshees) you let the player with the fresh profile do two barrel-rolls, one in each direction, and a loop-the-loop, and then finish the game as usual, you can then choose the Foundation map from the multiplayer, if you use that fresh profile. Anyway, I wondered if anyone knew any other glitches that unlock new multiplayer maps. I don't have xbox live, so I can't download new maps.