Stargate Atlantis/Nightmare Fuel


 * The Wraith: creepy-looking space vampires that suck the life out of you with their hands.
 * The black-shadow-cloud being from Hide and Seek absorbs energy and electrocutes you if you touch it.
 * The Iratus bugs: Sheppard has a very good reason for hating them, considering they attach to your neck, paralyze you, and slowly drain the life out of you.
 * Dialed up a notch when
 * The entire concept of Childhood's End:
 * Compounded by the fact that the belief was likely instilled by
 * The Hoffan drug: it kills almost exactly half the time, meaning that anyone injected has a 50% chance of dying.
 * Teyla's ability to  is pretty nightmarish at times, especially because if she's not careful, one of them can.
 * Later, when she's, a Warith queen she's attempting to control nearly
 * In Home, the "mist" that covers the planet is actually a race of sentient beings. This leads to several instances of Nightmare Fuel:
 * First, every time the Stargate activates, thousands of the mist beings
 * Second, the group is put into a  by the mist beings in order to prevent them from using the Stargate to dial Earth, but the mist beings have no clue (and later, don't care) that the team, as human beings,
 * The Nanite virus in Hot Zone that kills you in a matter of hours by infecting your visual cortex, causing terrifying hallucinations, then giving you a fatal aneurysm.
 * The AI Wraith virus in The Intruder kills anyone who attempts to expose its existence.
 * This leads to
 * The concept of runners is pretty terrifying. They implant a tracker in your back (where you can't remove it yourself), then set you "free," hunting you down like large game. Some of the runners, like Ronon, manage to avoid getting caught for years, but everywhere you go, the Wraith follow. You can never make friends or settle down or stop running because the Wraith will inevitably show up to destroy everything.
 * The implications of Duet: if Cadman's  would her body just have been reintegrated as a corpse?
 * Trinity: are they sure that solar system was uninhabited?
 * Conversion: involuntary, gradual loss of control over your own mind and body is horrifying enough. Now add in that you're losing control because you're slowly being turned into a monstrous giant bug creature.
 * So, as of Critical Mass, how long had
 * Griffin's death in Grace Under Pressure was pretty horrifying, more so for Rodney than anyone else. Not only was he suddenly alone in a sinking jumper with little remaining power (nightmare fuel by itself), but I can't imagine that the nauseating sound of the front section being flooded with Griffin inside (and the no doubt sickening mental image that resulted) will ever quite leave him alone.
 * Griffin's death in Grace Under Pressure was pretty horrifying, more so for Rodney than anyone else. Not only was he suddenly alone in a sinking jumper with little remaining power (nightmare fuel by itself), but I can't imagine that the nauseating sound of the front section being flooded with Griffin inside (and the no doubt sickening mental image that resulted) will ever quite leave him alone.