13 Ghosts

Gimmick: Illusion-O

William Castle, producer of popular horror films and thrillers in the 50s and 60s, became famous for his use of gimmicks, such as a skeleton emerging from a door in the theater (Emergo, used in "House on Haunted Hill"), buzzers in seats to give an impression of electric shocks (Percepto, used in "The Tingler)"  and a one-minute pause before the climax of the film (Fright Break used in "Homicidal").