Artifacts in general are Paranoia Fuel incarnate. Thanks to the powers they hold, even the most benign of artifacts can cause serious injuries. That's ignoring their appearances, which can be literally anything. In more than one episode, things like candles or books have killed dozens of people. Watch some of the scarier episodes in a row and you will start to get scared of things around your home.
As an example, one episode had a completely unremarkable glass jar cause a Zombie Apocalypse. It was sitting right out in the open in multiple scenes, but most viewers probably never even considered that it might be the artifact.
Claudia's scream/ Big "NO!" when she sees Steve's dead body. Crosses over big-time with Tear Jerker.
Ms. Fredrick dying. She rapidly desiccates in front us, pretty much being reduced to a mummy.
The three young archeologist's death in the first part of the season 2 finale. They end up being mummified aliveone by one.
The young woman we see getting turned into a glass statue.
"Don't Hate the Player" is, all in all, a very lighthearted episode with lots of nerd humour in it. You can imagine the Mood Whiplash, then, when the game starts exploiting the players' fears via its neural interface and we're suddenly "treated" to the sight of Claudia strapped to an asylum hospital bed, shrieking in abject terror as a doctor is about to apply a giant set of rusty electrodes to her head. The subsequent "Myka to the rescue" moment was sorely needed and could've happened a bit sooner. Allison Scagliotti is truly a gifted actress as, while Claudia's previous breakdowns were heartrending in their subtlety and understatedness (see S2 finale, scene near the end with Artie bandaged up), pulling out all the stops isn't a problem for her either - no Narm to be had here, just an all-too-believable portrayal of someone's worst fear putting them through the wringer. It doesn't help that the other fears were either played for laughs, introduced In Medias Res, or applied to one-off guest characters who didn't have much involvement. This one they showed in its entirety, and they lingered on it a bit too long for comfort.
"A New Hope" has Claudia trapped in a small dark space with no light and no way out and her legs are buried under rubble. She manages to have the presence of mind to tell the others to never mind about her because they're chasing after a giant reset button that'll make it so that she never got trapped in the first place. Followed up shortly by Pete's "I won't remember dying" discussion with Artie. HOLY CRAP. I've never been so grateful for a reset button.
Near the end of "Personal Effects", only five of the six loose artifacts were shown. The unseen one was a waffle iron whose waffles made your skin melt. How did they find this out? Why was it mentioned as an aside so nonchalantly?
Evil!Artie. Imagine MacPherson, only even more evil with a personal knowledge of the entire cast and a willingness to use all their faults against them.
Bronzing. Particularly the reveal that you're conscious the entire time.
Similarly, it's later revealed that before Paracelsus refined the technique, bronzing only lasted a few hours before the subject slowly began to crumble into dust. Imagine feeling yourself fall apart and being unable to do anything to stop it?! Talk about A Fate Worse Than Death!
The downside of the levitation artifact in "The Sky's the Limit". It can levitate anyone, but the last person it was used on flies up into the sky to either asphyxiate or fall to their doom. We even see one character rocket into the stratosphere while he screams helplessly. To anyone even mildly phobic of heights this scene can be...difficult to watch.
Mrs. Frederic choking Leena in "Time Will Tell". After the commercial break we find out it was to disconnect her from the Pearl of Wisdom, but the first time you see it there's no way to know. It's quite frightening.