District 9: Smart Guns That Read Your DNA

It's not much of a spoiler to say the aliens in District 9 have the snazziest trigger lock around. The Prawns, as they are known in the movie, have some strange ideas for safety, though. Their trigger lock is DNA-encoded not to keep little Prawns away from dangerous gear, but to prevent any other species from activating the weapons. (That's the sort of detail that raises all sorts of questions about just who the Prawns were fighting that they needed this kind of security, and whether the enemy also had DNA-locked rifles.)