In chapter 4, when going to the bridge, a Brute's head bursts through a black window at the side. After shooting at it, it will pull away. Directly above the hole in glass is a sign reads: "Visitors! Must sign in at guard house." Looks like someone made the guard pretty angry at newcomers.
The death animation of a Divider's head. After you've been decapitated, the head limply hangs from the base of your neck by its tendrils and lumbers off while trying to lift itself into a better position on your body.
The intro to the hydroponics level includes a massive Scare Chord... to some tomatoes being watered.
In the waiting room of the Ishimura Clinic in Chapters 2 and 5, one side of the room is in near-total darkness, but shining your flashlight on the wall reveals a lot of graffiti, including this gem:
Original line: WE ARE SO FUCKED
Later addition: Hey its ok to be fucked
Dead Space: mobile
In the Interquel for the iPhone, we get this gem from Tyler in Chapter 4:
Vandal: (Reaches a locked door.)
Tyler: Vandal, that door is on quarantine lock. You have to backtrack about 300 meters, take a right through the utility area, then GET OVER THAT MINE SHAFT AND... (chuckles) Just screwing with you! Try it now, lock's open!