While not the full game (impossible, since it's not even done yet), some enterprising types have managed to get hold of a demo for the upcoming Call of Duty: Black Ops 2. And proceeded to do what you'd expect.
Namely, we get a video with the worst soundtrack on Earth, obnoxious overlays of developer interviews and obtrusive watermarks.
While the footage - presumably lifted from a recent Black Ops II showing - is only limited to a bit of multiplayer, Activision has since confirmed to Kotaku that the footage is from "a development demo build", and that "the retail build was never accessed or compromised."
As for all that weird camera jumping, while the video was first posted on the YouTube page of a self-professed Call of Duty modder, and is angled as some "triumph" for hackers, Activision's statement says the trickery is the result of "developer tools meant for testing".
UPDATE - Story edited to reflect Activision's confirmation.
UPDATE 2 - We've heard the leak may have come from a closed internal beta, not a public showing.
iHcJames [YouTube, original video removed, thanks Chris!]