There are many firsts taking place in this installment. For the first time ever, a CoD game will have co-op. Cooperative game play can be with 2-players split screen or up to 4-players online. This led to the promise of more squad based elements during gameplay. Another first, swimming. Swimming will be available in both single player and multiplayer. One can no longer run through water, now the water plays against you making you slower.
According to Xboxfocus.com there are leaked images of possible box art. As with CoD4 box art, there were several options rumored before one was ultimately chosen. There are a few things that are bit peculiar with these boxes. One, there is a lack of the number 5 anywhere on any of the boxes, but this may be attributed with rumors of Activision wanting the game to be marketed as Call of Duty: World at War as opposed to Call of Duty 5.
Even more leaked information is making it's way to the internet. These are rumored to be screen shots taken from the game. 
Pictures from neocrisis.com
