Terminator 2 - my dad took me when it came out. Was young enough so didn't know how it was marketed but my mind was blown when it turned out Arnold was the good guy.
The Hangover - somehow had absolutely zero clue about this movie. Took a girl opening night and the entire crowd was in hysterics. One of the most fun crowds I can remember.
Avengers: Endgame - still get chills during the final battle.