Phantom Manor at Disneyland Paris. Hate to sound like a pussy but it's a long story.
Summer 2007. I was 5 years old. I mostly had a good day at Disneyland Paris...but my parents basically dragged me on Phantom Manor, which, as a lot of you coaster fans should know, is a bit darker and scarier than the California, Florida and Tokyo versions of the Haunted Mansion. I remember having my head down most of the ride, and when I looked up, it was that scene just after the Bride's Boudoir (the room where there is a large skull shape in a mirror) where the evil, skeletal Phantom can be seen, evilly cackling next to an open grave with an undead dog by his side.
After this one ride, my family never went near Phantom Manor for the remainder of the time we were there. I enjoy the ride now, but I still feel a little scared/nervous and get a little chill when I am walking up to the Manor's doors.