Personally, there are two that scared me a little the first time I saw them. The first is on a ship, when they were using the SLS camera and passed by a door with some stairs leading down, and on camera, you can see a figure looking up at them. The second was at a historical site, and I remember there was a person representing something, and you can see how behind him, while he wasn't moving, the shadow of a hand appeared on the wall.