I will admit that reading the High Octane Nightmare Fuel page over at TV Tropes because I couldn't sleep was very obviously a bad idea (look, I got there from the page for Sayonara Zetsubo Sensei, you know how that site works), so I now feel obligated to share with you the horrible mental images I am never going to be able to not think about:
The Enigma of Amigara Fault, a one-off manga that is probably more unnerving than 90% of the horror movies produced in the last ten years, and it doesn't even get to the really disturbing pictorial content until the very end. It's just. Maaaaaan. That is how you scare people, and that is a reminder of why I don't actually like horror very much and am going to desperately try to restore my mental health with gay porn now.