2. Facehugger Attack (Alien & Aliens)
Easily one of the most iconic antagonists in science-fiction history, the facehuggers made their first appearance in Alien and have made people even more terrified of spiders ever since. John Hurt's Kane is the first to fall victim near the start of the film, with it attaching itself to his face and implanting an embryo; for added protection, it will attempt to strangle the host if an effort is made to try and remove it from their face. In Aliens, there's a brief and brilliant close-quarters fight between Ripley, Newt and a facehugger, a nerve-shredding sequence which demonstrates the facehugger's ability to not only be fast and strong, but also smart as it attempts to get the better of Ripley (and very nearly does). The Half-Life games have already shown how well this type of enemy can be implemented into video games; the headcrabs are essentially a non-subtle nod to the Alien franchise, and if Gearbox are able to imbue their game with the same sort of terror (the Ravenholm level in Half-Life 2 is still one of the most terrifying things I have ever played), then this will be an appropriately hair-rising experience.