This is based on opinion. Please don't list it on a work's trope example list.
Nightmare Fuel / Carnivāle
In the very first episode, we have a woman spouting dozens of silver coins from her mouth, a woman choking to death from dust, and it rains blood. Other creeptastic scenes include living Madonna and Child statues bleeding from stigmata, a man being tarred and feathered and left to die in the desert, the most inbred family this side of Deliverance and "Home" kidnapping and torturing their distant cousin, Justin's hallucination of peeling off his face to reveal his enemy - Ben, and Evander Freaking Geddes (please do not ask. Most fans have repressed.) Then there's Ben's dreams - practically an alphabetized Nightmare Fuel list - including the scenes where Ben experiences the Russian's very graphic triple amputation and the dream where Justin and Iris are feeding their congregation razor blades as communion wafers and blood drips out of their mouths. On the flip side, we have Justin's rebaptism, his mind control of the patient in the mental institution to repeatedly bash his head against a wall in punishment for speaking over the radio, the scene where he decapitates Scudder in the car and then holds the severed head up, licking the blue blood running down his arm and his driving the maids insane, apparently by using demonic sex.
But by FAR, the creepiest scene in Carnivale had to be at the end of "Pick a Number", where the Carnivale packs up to leave Babylon, and Samson looks back at the saloon to see the ghost of Dora Mae standing at the window, where she is then embraced by one of the men and pulled back into the shadows. A naked Dora Mae. Not creepy until you realize that the curse Scudder laid on Babylon means that while she did die, she's still alive at night, and must stay with the creepy rapist murdering miners to be their plaything for all eternity.
Nevermind the sheer squick factor, when we finally see Management/The Russian/Justin and Iris's father and very soon there after Ben kills him because somehow, even though he has no limbs, he can still jump onto Henry Scudders's back and try to kill him... brr. I still sometimes see Lodz in my dreams... "Have you seen my bear?"
Actually, the Russian has one arm. He wraps it around Scudder's neck, and earlier it's shown (or at least implied) that he can hold a cigarette with it.
In "Hot and Bothered", when Sofie is told "Every prophet in her house", first by one of the Templars, then by a little girl on the road, both with the black eyes.
In the first season finale, "The Day that Was the Day", Ben decides to slit his own throat as the exchange for healing. Luckily, Scudder is around to clean up the damage, but ugh . . .
Then in the series finale "New Canaan", Sofie is being held captive by Brother Justin in a remote cabin. She begins to have horrible visions, such as Brother Justin raping her mother. Then a veiled figure, who Sofie thinks is her deceased mother, approaches her. When the figure lifts up her veil, it is Sofie herself, but with coal-black eyes. Sofie gasps as her demonic self tells her, "This is your house."
And let's not forget Brother Justin, slashing his way through a crowd with a scythe as he quotes Ezekiel, even eviscerating Reverend Balthus, who had raised Justin as his own son.
Evander Geddes! EVANDER GEDDES! HE WILL STEAL YOUR FACE! LIKE KOH! ONLY KOH ISN'T AS CREEPY!
Brother Justin raping his maid. Complete with beasty noises. And bite marks on her body!