Early in the movie Prometheus, while most of the crew is still in cryosleep, David makes the rounds of the ship.
While walking from one room to another, David seems surprised to see something on the floor of Prometheus. He stops to pick it up and looks at it quizzically.
What did David stop to pick up and look at?
I just took it to be a bit of fluff or dirt. This seems to be just another piece in a greater montage showing the tediousness and repetitiveness of David's two-year wait for the ship to reach its destination. The picking up and looking at the speck just adds an extra, fastidious, layer to David's personality and is further evidence of Fassbender's compelling performance.
Think of Niles picking a piece of fluff off his pant leg in Frasier ;)
