9. Stealth Genome Soldiers
Metal Gear Solid 1's genome soldiers aren't the most frightening enemies. With their battle cry of "Huh? What was that noise?" and their tendency to follow footsteps in endless circles, they're easy to evade or take down.
In the second half of the game, things take a turn.
When Otacon calls Snake and reports unexplained presences in the communication tower's elevator, before frantically warning of the presence of stealth using genome soldiers, it's almost a "call coming from inside the house" moment. While the eventual boss fight isn't too difficult - what's four genome soldiers to a guy like Solid Snake? - the slow build to the ambush is a fine piece of slow burn gaming horror.