Scenes in movies thast blew your mind as a kid.

[Svengoolie 3]

This scene in WotW. For a kid this was scary.

https://youtu.be/G5H4yK_tiGI?t=243

[Trevor]

The scene in which Jean-Pierre Cassel comes into Richard Widmark's compartment on the train in Murder On The Orient Express and switches off the main light: the blue night light goes on, turning everything blue and then Jean-Pierre comes up out of the darkness with a malicious expression on his face. Scared the crap out of me when I was seven. 

The montage with the eerie score which follows the main titles of that film are also creepy.

[Gabriel Knight]

The scene in Masters of the Universe where He-Man is flying on that overboard thingy. I remember being extremely excited waiting for that particular moment. I watched it recently and to be honest I enjoyed it a lot, it's a great movie.

[Alex]

Jaws when Quint gets eaten alive.