Uhm... For me it is properly Sanitarium. Due to my profound interest for dream interpretation, I couldent help but to constantly overstrain myself, trying to decipher the enigmatic nature of the story, which was spooky beyond measure. Attempting to unravel this psychotic nightmare for days, also left me somewhat ungrounded... Im glad it was only a 20 hour game, had it been twice as long I would properly have ended up in a bin somewhere.
Also, the broodmother quest in DA 1? Just as terrifying as seeing the clown from "It" for the very first time.(In television, that is. A real life encounter would be scarier than anything fiction could provide.)