The Cheerleader: Played with. The head cheerleader is kind of bitchy, but it has more to do with the fact that she's an immortal witch planning to suck the souls of the student body then her being a cheerleader.
Erica. To be honest, after the pilot movie Erica immediately starts to suffer of Badass Decay and ends up being useless most of the time: she bares her fangs to the Monster of the Week and the next thing we see is that she's been knocked out, transformed into a doll or hypnotized. Or trapped in a van. Said decay is probably a consequence of The Worf Effect, though. Rory is equally useless too, most of the time. It's more of a subversion ofThe Pirates Who Don't Do Anything, in that Erica makes it perfectly clear that she does feed on humans (and says as much in "Flushed" and "Village of the Darned"), but we just don't see her do this on screen. The ending of "Friday Night Frights" directly implies that this is also Kurt's fate.
The two girls from the martial-arts club in "Smells Like Trouble" also qualify.
Downer Ending: "ReVamped". More like a Bittersweet Ending, because even though Sarah is a full vampire, the last shot (as she flies away) shows that she may get used to some of the benefits, and there's no doubt that both she and Ethan realize how much she cares for him. Also, it's not as if it'll change her life in the immediate future (she can still do the things she has before, like Rory and Erica still do), drink the blood substitute or animal blood as before...
'80s Hair: Doug Falconhawk is rocking that mullet (even though it's only a wig).
Either World Domination or Something about Bananas: In the season 2 episode "Hottie Ho-Tep", Mr. G is reading some hieroglyphics by a mummy, and says that it translates to a declaration that his spirit will never go to the afterlife without finding his true love... either that or it's cleaning instructions.
Confirmed in "Welcome Back Dusker", when a vampire sent by the Vampire Council specifically points out that they'll go after Sarah's 'vampire-hunter boyfriend' (namely, Ethan) if the vamp-on-vamp attacks continue. Also, one of the seniors in "Flushed" tells Ethan that "his girlfriend is polluting the bathroom" (because Sarah is still feeling the effects of drinking too much blood).
In "The Date to End All Dates, Part 1", Jesse seems mildly impressed (and not angry) when he finds out that Ethan is out on his first actual date with Sarah.
Evil Costume Switch: Erica's clothing choices after she's bitten in the pilot movie. She even lampshades this as a reason for wanting to become a cheerleader and wear the uniform.
Eye Scream: The reporter in "Lawn of the Dead", when Tiberius attacks him on-camera.
Family-Unfriendly Death: In the pilot movie, Jesse actually sucks an Innocent Bystander's blood dry and collects her soul in a Soul Jar, with most of the act being shown onscreen. Kate (the freshman girl in "Flushed") has a particularly gruesome end in the girl's bathroom.
Friendly Neighborhood Vampire: Sarah. And how. She's probably has the strongest moral compass on the show, is often referenced as a wet blanket, and always sticks up for the little guy. Also played with in Rory's case.
Freudian Excuse: Before being turned Erica was a Hollywood Nerd who took a lot of crap. Afterwards she decided that this justifies her being a bitch.
Glory Days: Benny's Grandma touches upon this in the movie, when she says that after living in Whitechapel for almost a century, one learns a few things.
Heartbroken Badass: Sarah, as of the end of the season one finale. She gets better, though.
Hell-Bent for Leather: The only way we could tell Evil!Benny from Benny prime was the evil clone's leather jacket. Mostly, it's an aversion though — Sarah and Erica have leather jackets but don't wear them often and they wouldn't fit the boys' Hollywood Nerd image, making this one of the few supernatural-themed teen shows that doesn't drape the whole main cast in black leather.
Sarah: Whatever you saw, it's not what it looks like! Ethan: You're a freakin' vampire, who eats animals and drinks their blood! Sarah: Okay, so it is kinda what it looks like.
Played straight in "Smells Like Trouble", when Ethan's father listens in on Ethan and Benny's webchat.
Oh Crap: Ethan's reaction when he realized that Doug knows Sarah's a vampire in "Doug the Vampire Hunter.
One of Us: EVERYBODY in the main cast (as they're all Genre Savvy) — even though Sarah tries to pay lip service to being a Cool Loser. Erica and Sarah call each out on it in the vampire hunter episode, when Erica mentions that Sarah made a Star Trek reference — and Sarah shoots back that Erica recognized it for what it was.
Seers: Ethan (and it's insinuated in The Movie that that it's a familial trait, so his children might have the same gift). As of the end of Season 2, Ethan's powers have evolved to outright Telepathy by touch.
Stealth Mentor: Benny's grandmother qualifies as of "Independence Daze", considering that she sent Benny, Ethan, and Sarah into alternate dimensions to face their individual worst fears, all to teach them a lesson about working together.
Title Drop: In the TV movie pilot, by Ethan after he and Benny see recently vamped Sarah sucking the blood of an animal.
Token Evil Teammate: Subverted by Erica. She's got both the general disregard for the well-being of others and the willingness to use her powers selfishly, but her friendship with Sarah prevents her from going over the edge, as does the fact that Sarah is Genre Savvy enough to keep an eye on Erica whenever she suspects she might be up to something.
Translate The Loan Words Too: Sort of. When Benny gets transformed into his costume, El Merlo Loco, in the halloween episode, the subtitles refer to him as "The Crazy Merlo," which is what "El Merlo Loco" means, even though even in English he's referred to as "El Merlo Loco".
Vampire Bites Suck: The one time we see someone bitten onscreen, Ethan ends up writhing on the floor in agony until the venom is sucked out.
Weirdness Censor: You'd think that Ethan's parents would have noticed and commented of some of the ongoing weirdness. Also, the local news and the school's administration haven't seemed to catch on to the weirdness.
"ReVamped". Jesse returns from the dead, brainwashes Erica, and bites Ethan to force Sarah to become a true vampire by sucking out the venom.
"The Date to End All Dates, Part 1". Ethan and Sarah go out on their first date, Ethan works with both Jesse and the Vampire Council, the Vice Principal is revealed to be the being that attacked the kids in "Independence Daze", and he gets hold of a device that can kill all of the vampires in Whitechapel.
"The Date to End All Dates Part 2". Ethan, Benny, and Sarah team up with Jesse to stop Vice Principal Stern, the Vampire Council evacuates the city, Ethan and Sarah may or may not of gotten a Relationship Upgrade, and the Lucifractor explodes, possibly taking the whole city with it, leaving the fates of our heroes (and Jesse) up in the air.
"What Do They Fear?" Episode: "Independence Daze". In order: Sarah — a version of herself who feeds at will, without restraint or conscience. Benny — A cyborg dentist from one of his favorite movies. Ethan — Losing the people he cares about.
Who Wants to Live Forever?: Sarah's view on being a vampire. Half the season is her trying to find a way to regain her humanity through magical means. Other vampires actually taunt her on this, with one vampire specifically mentioning that she'll probably forget about Ethan and Benny after a couple of centuries, and Sarah herself saying that they will move on, get married and live fulfilling lives, while she will be 17 forever.