The teaser trailer for Call of Duty 7 is here, called Call of Duty Black Ops. There's no gameplay to be found in the trailer, at least, no discernable gameplay, but what is there is a mysterious plot element. It hints at something sci-fi almost with an offscreen character laying on an operating table mixed with flashbacks of different battles and locales.
The sci-fi element comes from the last line of the trailer, spoken by an unseen "Doctor." Call of Duty Black Ops launches November 9th and will feature some form of co-op, though we aren't quite sure what yet.