A Halloween costume consisting of a simple hockey mask and dark clothes can be enough to scare people at Halloween thanks to the Friday the 13th movies.  Friday the 13th is a horror movie franchise similar to Halloween and A Nightmare on Elm Street.  Developed in the late 1970s like Halloween the Friday the 13th franchise was intended to be a series of slasher films built around one psychotic character. The original creator of the film was Sam Cunningham, who had a strong background in horror films. Cunningham had worked with horror master Wes Craven on the iconic horror film The Last House on the Left but wanted to distance himself from that film after the public outcry against the film. 
In the original Friday the 13th film counselors at Crystal Lake summer camp are stalked and murdered by Jason Voorhees, a child that had drowned at the camp while two counselors who were supposed to be watching the kids were having sex.  At the end of the film one of the counselors manages to decapitate Jason before dying and the audience learns that the killer isn't really Jason Voorhees, it's his mother Mrs. Voorhees, who has been killing the staff at the camp out of a desire to avenge the death of her son. 
In the next Friday the 13th film the real Jason Voorhees begins killing counselors and staff at the camp out of a desire to avenge his mother's death. Towards the end of the second film one of the hunted staff finds a cabin in the woods that Jason has used to make a shrine to his dead mother. The centerpiece of the shrine is her decapitated head, showing that Jason has no intention of ever ending the carnage at Crystal Lake. 

Unlike the Halloween franchise, which attempted to have a thread of continuity connecting most of the films that were built around the central character Friday the 13th is known for fantastical plot lines like Jason Voorhees being replaced by several copycat killers over the years and even being frozen cryogenically and returning from entombment aboard a space ship to Crystal Lake camp to begin killing again.  The reason why the copycat killers are able to take on the Jason Voorhees persona is because they begin wearing a hockey mask like Jason wore to kill his victims. The hockey mask, like the William Shatner mask donned by Michael Myers in Halloween, has become a piece of pop culture history.

Jason's hockey mask is one of the most widely recognized items in pop culture. In the film franchise Jason doesn't actually begin wearing the mask until the third film. In the second film where Jason first appears as a main character makeup is used to create his unique look. In the third film the hockey mask appears and becomes the device used by all the copycat killers to portray themselves as Jason Voorhees.  A simple hockey mask can be a great Halloween costume because it's universally recognizable as the trademark of Jason Voorhees and Friday the 13th.