Adults Are Useless: The counselors know Artie is a pedophile and don't seem to care. The head of the camp is more concerned with the bad publicity and possible lawsuits that might arise from homicides than the fact that there's a potential murderer on the grounds that are filled with kids.
The aunt. DEAR GOD, The Aunt.
Alpha Bitch: Judy. She seemingly goes out of her way to be bitchy and hostile toward Angela.
Asshole Victim: Most of the victims. Most notably Artie the cook, who really likes children (yes, in that way). Ironically, he's also the only victim who doesn't die. Though if he survived his grave injuries it's likely a A Fate Worse Than Death. He's horribly disfigured and likely blind by the time he's rolled off to hospital. However some of the victims are selected for very petty reasons, most notably the young children murdered for being a bit bratty and kicking sand at Angela.
Ax-Crazy: The killer has a lot of pent-up aggression as shown by the brutality.
Bee Bee Gun: Billy is stung to death when a beehive is dropped into his bathroom stall.
Bigger Bad: The demented Aunt Martha took a mentally fragile boy and forced him to be the daughter she always wanted. Worse still this involved pretending to be his recently dead sister. Add in the trauma of losing his family and being raised by a lunatic, Peter ends up becoming a psychotic serial killer.
Butt Monkey: Mozart who is on the receiving end of several pranks in the boys cabin.
Chekhov's Gun: Aunt Martha gives Ricky and Angela signed physical examination forms so they can go to camp. There's a good reason she doesn't want another doctor taking a look at Angela...
Freudian Excuse: The killer's family died in a boating accident and his aunt forced him to dress in women's clothing and otherwise pretend to be her niece, who she preferred but actually died in the accident.
Groin Attack: Strongly implied to have occurred on a female. With a curling iron to boot! However whilst the scene indicates the possibility, it never explicitly shows what happened.
Harmful to Minors: Angela witnessing the death of her family. Well, Peter witnessing his father and sister's deaths more accurately.
Has Two Daddies: Angela's dad's boyfriend didn't get custody after the accident.
It's All About Me: Judy is incredibly self centred, insecure and jealous. Her ego is so massive that she becomes envious of Paul and Angela despite having several other men fawn over her constantly. Apparently the idea of a girl who isn't like her, that also has a man's attention, just rubs her the wrong way. Interestingly it's implied that before she hit puberty she wasn't such a jerkass with a high opinion of herself.
Peek-A-Boo Corpse: Several victims are discovered this way. One beneath a boat and another corpse falling from behind a shower curtain.
Reasonable Authority Figure: Ronnie, the buffed-up, muscle-shirt-wearing counselor, really does care about the kids and their safety in the face of the killings, far moreso than the selfish, asshole owner of the camp. He gets a Pet the Dog moment early on when he politely tries to get a homesick Angela to eat her lunch.
Red Herring: Hints that Ricky is the killer. While this is obvious to the more Genre Savvy viewers it later works in the films favor, as The Reveal is more terrifying. There's a twist, just not of the nature you thought you were getting. This was all made more confusing by the fact that Ricky's actor did all the 'kill scenes'.
Right for the Wrong Reasons: Mel soon connects the dots as to why the victims are being targeted. They have all wronged Angela. But then blames the wrong person. He suspects Ricky is murdering people out of some twisted desire to protect Angela. When in reality "Angela" is actually killing them personally.
Sickeningly Sweethearts: Everyone makes fun of Paul and Angela for being this. They sort of are for a while until the end.
Shadow Discretion Shot: Judy's death. We don't explicitly see what the killers done, only that it involves a curling iron and an awful lot of pain.
She's All Grown Up: Played With. Paul, in an admittedly juvenile manner, points out to Ricky that Judy's hit puberty since last they met. However she doesn't think Ricky's any good for her now that she's "more mature" and Ricky takes an instant disliking to her new found personality.
Villainous Crossdresser: Angela is actually Martha's nephew, Peter; the crazy old bat, upon winning custody of him, forced him to dress up as and pretend to be a girl because she wanted a girl and not a boy.
Aunt Martha: Angela. Such a lovely name. Why I believe it means 'angel'! Why, yes, I'm sure it does! I know you're going to like that name, won't you, Peter?
Your Cheating Heart: Paul kissed Judy while he was trying to build a relationship with Angela. Though he regrets doing it immediately. Needless to say, Angela wasn't happy about this, and made him the last victim of the film.