The user either is or can become a Halloween entity, personification of Halloween and its variations. The powers of a user can differ greatly based upon what aspect of the holiday they take the shape of. They do not necessarily need to be one of the traditional holiday entities.
Halloween Town (Tim Burton's The Nightmare Before Christmas)
Sam (Trick r' Treat), the vengeful spirit of Halloween.
The Summerween Trickster (Gravity Falls) is a malevolent being made of candy that stalks Summerween night.
The Fright Knight (Danny Phantom), Spirit of Halloween and former herald of the Ghost King.
Jack o' Lantern (Valkyrie Crusade)
Halloweenie (Channel Awesome)
From left to right. Hollow Jack, Boogeyman and Candy Corn Scarecrow (The Barn) are a trio of killer monsters that embody the darkest side of Halloween.
Jack Skelington (The Nightmare Before Christmas)
SCP-2331 - SCRAVECROW (SCP Foundation) was the personification of the Halloween season until he grew disillusioned by the over commercialization of the holiday and decided to retire so he could become a disc jockey.