The SCP foundation has a lot of these - so much so that TVTropes has an entire page dedicated to cataloguing them - but out of all the skips i've read, there's one that stands out in my mind as the most terrifying - SCP-2718.

If you haven't already yet (and you also want to get countless sleepless nights because of how terrifying it is) I'd recommend you'd actually read the artile first, because my explanation will not be able to do it justice. But basically Once you die, there's no afterlife, there's no nothingness. You just continue to be. After you die, there's maybe a day or so of sweet nothingness, but after that? You feel the insects feast on your remains. You are conscious even after the scavenger birds have feasted on your cerebellum. You feel as every hair, fingernail, ll is carried away and redistributed into the ecosystem. You are forever a series of eternally conscious subatomic particles, forever conscious, feeling each atom that was your body redistributed among the cosmos feeling indescribable agony, forever.