Aliens
There was no other science fiction film like it, seemingly modern day Marines versus the most iconic looking monster/s. It wasn't just a good action film as so many like to say, it was genre defining
The trailer itself evokes memories of feeling excited with anticipation, I was 12 at the time.
The screen going black and then the red lighting with an exasperated Hudson questioning how animals can cut the power.
For the movie itself I can vividly remember where I was sitting in the theater and everyone deathly quiet when Hicks pokes his head up through the ceiling grate with a flashlight - at which point someone yells out "Peekaboo!"
So, yeah,
Aliens.