In the majority of sci-fi films, death is expected. Usually, you can see these deaths coming a mile off. Sometimes it's clear as soon as you see the character; they're annoying, or uninteresting, or cocky, or rude, or all of the above, and you know they won't last long.
This can sometimes dampen the deaths themselves. You know it's coming, it happens, and it doesn't effect you. The best deaths are the ones which throw you off. Be it characters killed off too early, big named actors dispatched with little care, or the end of a false protagonist, deaths in the world of sci-fi are much more effective when you don't know what's happening - when you have to pause the TV and re-wind the scene just to make sure it actually. Just. Happened.
The following list will have a look at the most sudden, out of the blue deaths ever put to the screen in a sci-fi film, from game-changing monster kills, avoidable demises and brilliant plot twists.
Naturally, major spoilers will follow. In any case, enjoy, and make sure you never lock yourself in a room with an alien...
10. Kane (John Hurt) - Alien
Okay, okay, yes - this is an obvious pick. Of course it is. But there's a clear reason for that. Just recall the first time you saw Alien. You knew little about it, you didn't how things were going to kick off. And the next thing you know John Hurt is convulsing and a little alien is popping out of his chest. Everyone's reaction is the same the first time they see this iconic moment of horror - confusion, shock then disgust.
And more confusion.
The sudden demise of Executive Officer Kane is shocking on its own, even forty years later, but the sheer unexpectedness of the scene is dialled up by the fact that going into the film, it was John Hurt who was the big star; the actor who people wanted to see because he had already made his mark on the world of film thanks to Midnight Express (for which he received an Oscar nomination).
So when the alien bursts out of his chest, and at such a happy and light part of the movie, it's purposefully done to shock and appal. And it's safe to say it pulls it off.
The scene gets bonus points for the cast reactions. None of the other actors really knew what was about to happen, and their response is the real deal. Veronica Cartwright (who plays Lambert) passed out when the cameras stopped rolling. So we can rest assured we weren't the only ones thrown off by the death.