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.
There's a conversation between Jack and Marcy that has nothing to do with anything really and has no impact on the plot. Just before going into the bunks to do it, they have a talk by the lake. Marcy tells Jack about a dream she frequently has where it's raining and the rain turns to blood.
Right before she's killed, Marcy is in the outhouse and randomly looks into the mirror to do a Katharine Hepburn impression, quoting The Rainmaker.
Critical Dissonance: Critics more or less hated it, but it went on to be one of the biggest slasher films ever made.
Believe it or not, Jason Voorhees. He's dead and only appears in a dream sequence and flashback, but is one of the most memorable parts of the film. So much so he became the Big Bad of the franchise starting with the second film and became one of the most iconic slasher villains of all time.
Crazy Ralph is very memorable among viewers thanks to his over the top paranoid demeanor.
Epileptic Trees: Before Brenda dies, she's lured to her fate by the sound of a child calling for help. When we see "Jason" talking through Pamela's voice, Pamela just uses a slightly higher version of her voice, nothing like the child. Another thing to note is that when Brenda's body gets thrown through the window, it would have been difficult for Pamela to run to her Jeep from that distance from the cabin right before she meets Alice. When Pamela sees Brenda's body, she apparently feigns innocence by wondering who did that to her before immediately dropping the act to chase Alice. This has led some to theorize that it was actually Jason that killed Brenda rather than Pamela.
First Installment Wins: While there are several fans who prefer the fourth or sixth film over the original, this is widely considered the only genuinely good film in the series and the one critics are most likely to give good remarks on.
Harsher in Hindsight: Alice getting stalked by psycho-killers is uncomfortable to watch if you hear about Adrienne King's bad experience with a Loony Fan after the movie came out - and it made her quit acting.
It Was His Sled: By now, the twist regarding the killer is pretty well known, especially thanks to the opening of Scream (1996) famously spoiling it.
Jerkass Woobie: Pamela Voorhees. The novelization implies she only went on a killing spree to save further campers from Jason's fate. Betsy Palmer even viewed her as one, giving her a sympathetic backstory that involved getting disowned by her parents for a Teen Pregnancy.
Narm Charm: Mrs. Voorhees alternating her voice between her own and "Jason's", due to it selling how far gone she is.
Tear Jerker: The villain isn't Jason, but rather his mother Pamela, who went completely insane after the supposed "death" of her son. Then the ending and the sequels reveal he was never dead to begin with, meaning her horrible deeds accomplished nothing — except to inspire an innocent child to become a violent serial killer in her name.
The film uses Death by Sex to kill off the characters, but there's an in-story justification for it. Jason drowned while camp counselors were fooling around, so hatred of any kind of sex is his mother's Freudian Excuse.
Alice is the Final Girl but lacks many of the characteristics associated with what the archetype would eventually become; she still smokes and drinks with her friends, she's about to strip off on screen when the storm interrupts her (and she gets into a bikini earlier) and she's implied to be having an affair with Steve. She's only more responsible than her friends because she appears to be in charge at the camp.