Smell-O-Vision/Scratch and Sniff/Odorama: It is exactly what it sounds like. At certain points while a movie was playing, different smells would be either pumped into the theater or the screen would indicate which odor to scratch off the sets of cards that were handed out beforehand.
Percepto: This was a gimmick used by horror director William Castle for his 1959 Vincent Price film The Tingler. Electric buzzers were attached to some of the seats where the movie was playing. Towards the end of the film, the “Tingler” monster is shown escaping into theater, at which point the buzzers were turned on by the projectionist, literally shocking audience members.
Sensurround: This gimmick involved movie theaters installing special low frequency speakers that would cause the theater to vibrate and shake in an attempt to simulate the feeling of an earthquake.
Barf Bags: A gimmick used by some horror movies, like The Exorcist (1973) and Bite (2015).
Waiver form/Life Insurance: This was mainly used with horror movies. Audience members would have to sign a waiver saying that they accept all responsibility if they should die of fright during the movie. William Castle, already mentioned above with Percepto, took this a step further with his 1958 film Macabre when he gave audience members an $1000 life insurance policy in case they were scared to death by the film.