7. Cherubs (Doom 3)
Whether it's in a film, a book or a video game, monsters that resemble children are always going to end up high on a list like this. Compounding the terror is that, at first glance - albeit a quick first glance - these creatures simply remind us of the cute cherubs we've seen in cartoons and children's books, that is until you look at their limbs and lower torso, and notice the claws and monstrous lower-halves they're sporting. What's more, they have wings that allow them to hover towards you, and they let out an unpleasant hissing noise that is impossible to forget. The only saving grace is that, compared to some of the enemies you'll face later in the day, these beasties aren't too difficult to kill, but that's the genius of it; their grotesque design scares us before we even get to gauge how much of a threat they are.