Masks

Masks is used and seen a lot throughout horror films. They are used for hidden identities and often it is the villain that uses them.
In Friday The 13th the villain, Jason, uses a cloth to hide his identity until later in the film, he kills a victim and finds a hockey mask which becomes his trademark for the film. Masks are often used in the horror film posters or would be featured in it as it gives off a scary vibe.

In Scream, the stretchy ghost mask is used and if we were to see it, we would know who it is straight away.

I think using masks in horror films are extremely effective as this can really spook the audience and hide the villain's identity until later on in the film in which the 'final girl' somehow whacks it off the villain's face for a brief moment..