Forgive me because the post that I'm about to type is rather vague in description, and because I'm a lazy ass person that can't be bothered to find the exact source and description of what I'm posting, this may not make any sense
The gun which is named "Sally" is a callback to Nazi Zombies, and how one of the characters always called his gun Sally. The notches (or Tallies) were some kind of code that was intended for a GameStop promotional poster competition. Also loosely related to GKNOVA6 (from what I remember.) The notches revealed a website, and the website revealed a phone number.
When the phone number was rang, a sound very similar to the one that the random weapons box makes played, this in itself was another code, which when decrypted and told to a GameStop employeee would reward the person with a prize.
I'm doing a dual commentary with a friend very soon and we were planning to just talk about the multiplayer trailer and speculate on it, but he pointed me in the direction of GKNOVA6 which looks way more intresting.
I also think that at least one of the missions will revolve around the assisination of JFK. This is A) Because a GKNOVA6 transmission reveals a letter sent from JFK, and B) Because just after the voice over in the first reveal trailer says "A lie is a lie, just because you write it down and call it history doesn't make it true." The same letter is shown, with some black marks over it.
Also, there's two times in that trailer that you can pause the video and a zombie can be seen, the first shows a zombie lurching, the second shows one wandering, looking confused. All rather intresting, I'll link to the video when I make and upload it to YouTube.