Scream
The 1996 meta-slasher changed the genre forever, outright acknowledging that its characters—much like its appreciative audience—knew that slasher movies live and die by a set of well-defined rules. There’s a reason the series is still going strong in 2023; though it has certain elements of parody to it, the Scream franchise also always manages to be the very thing it’s satirizing, delivering genuine frights and gore with the best of ‘em.