Below is an official teaser image from the Call of Duty website. Apparently, a new teaser image will be released every few days.
As you can see, the picture isn't exactly clear enough to make out what it is. HOWEVER, the smaller thumbnails for each teaser image do flash between a fuzzy/darkened version and a more-detailed/brighter version while they are all listed together. Fortunately, somebody was able to grab a quick screenshot of the picture while it was flashing, which means that we get to see a clearer (although much smaller) version of the image.
See that? Doesn't it look remarkably like the Quadrotor (which was conveniently covered by FPS Russia today). Here's a picture of FPS Russia with the Quadrotor:
In case you didn't know, the Quadrotor is a controllable drone that can fire an SMG. At the end of his video, FPS Russia tells us that he's been told it will feature in Black Ops 2. Judging by the pictures above, he's right. My guess is that it will be a controllable killstreak!