These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Big Lipped Alligator Moment: When a policeman shows up at the camp looking for Crazy Ralph, it is badly timed to Ned running out of the cabin dressed as an Indian, screaming and dancing around. He says "oh shit" when he spots the cop but the characters don't bat an eyelid. It adds nothing to the plot and is just so random.
Critical Dissonance: Critics more or less hated it, but it went on to be one of the biggest slasher films ever made.
It Was His Sled: The killer is probably known to most people who are familiar with the series. Though to those unfamiliar with the series, they still might be surprised to see Jason's lack of appearance.
Narm Charm: Mrs. Voorhees alternating her voice between her own and "Jason's".
Jerkass Woobie: Pamela Voorhees. The novelization implies she only went on a killing spree to save further campers from Jason's fate.
One-Scene Wonder: Crazy Ralph appears twice in the film, and steals the show both times.
Seinfeld Is Unfunny: Averted. Although the end of the film ripped off Carrie which has become an example of the trope, fans do find the ending to the film scary.