Well the first gameplay footage has been revealed for BioShock 2 last night on GameTrailers TV. Check it:
All I have to say is that it looks awesome and I can't wait.
If you don't know anything about the game, it takes place 10 years after the original BioShock. You play as the first Big Daddy and the main enemy is the Big Sister who was a little sister in the original BioShock and has taken over Rapture.