As a morbid hobby, I look at crime scene photos online. It's sort of amazing the gory, frightening detail these photos exhibit.
Usually none of them has much effect on me, since I plan on joining their ranks in the dead soon. However, there was one photo of a Jeffrey Dahmer victim. For some reason, Dahmer had the man's body in a bathtub, mostly balanced on the side edge of the tub. One leg was inside, one was outside of the tub. The stomach and internal organs were gone. The ribs were exposed as most flesh was missing from them.
This photo stuck with me for some reason. Everytime I bathe, if I close my eyes, I see the unfortunate victim there, as if he were in my tub. When this happens I open my eyes as fast as possible to make sure I am alone. Then I dash from the tub, grabbing my towel on the way out, and run to my bedroom.
I don't know why this photo had such a strong effect on me, but I do know that I won't look at it again. I won't have to, as it's etched in my mind's eye.