Thoughtful question. wink
When I was 9 or 10, I went by myself to a decrepit old movie house in my Brooklyn neighborhood to see "Son of Frankenstein" (1939). The scene when the monster appears in the little kid's bedroom absolutely paralyzed me--I had a real hard time getting to sleep after that.

Possibly the most creative, scariest, nauseating scene ever filmed is in John Carpenter's "The Thing" (1982), when Dr. Copper applies CPR to Norris and unleashes his head from his gut:

https://www.youtube.com/watch?v=JjIXwkX1e48


Ntra la porta tua lu sangu � sparsu,
E nun me mporta si ce muoru accisu...
E s'iddu muoru e vaju mparadisu
Si nun ce truovo a ttia, mancu ce trasu.