I just watched the trailer and I've seen an AA-12 and a P-90. As a reply to ColdBloodBarrel, the AA-12 is NOT just any shotgun, I'm thrilled that they actually include this weapon (petty, though, I don't have a 360).
The AA-12 is THE
shotgun of shotguns. Not only is it the most accurate one, it packs quite a punch at a fast rate. In real life, you can put a lot of different types of ammunition in it.