Yes, Prometheus left a lot of narrative threads hanging, but many of these aren't really too important. One that we've been curious about though is what exactly it was that David said to the Engineer before it (spoiler alert) WENT BATSHIT AND STARTED KILLING PEOPLE.
According to the real-life linguistics consultant who appeared in the film, the words spoken were simply: 'This man is here because he does not want to die. He believes you can give him more life.’
Big deal, you say. But more intriguingly, Ridley Scott apparently shot a conversation between the two characters, rather than just these two rage-inspiring lines. Something else for the Blu-ray perhaps...
There's a bit more info you can check out here at www.thebioscopist.com, including how dedicated Michael Fassbender was to his character (hint - quite).