Three houses immediately come to mind for this thread!
The first was the home of a doctor/amateur taxidermist. The upper two stories were totally normal, bland, blah "trying-to-sell" decoration. The basement...was another story. As you walked down the carpeted steps, you were greeted by a stuffed lynx at the bottom. There were various other stuffed animals around the basement, most of which seemed to be endangered (there was the lynx, a bobcat, and a bald eagle down there, plus assorted deer heads). When you walked into the laundry room, there was a weird little extension that, at first glance, seemed like they might have tried to build a shower back there and only finished halfway (drain and walls, no water piped in). DH noticed what appeared to be blood in the drain, and we realized that was where the doctor/taxidermist dressed his kills! I could barely walk on the carpet after that. Ewwww!
The second had floor to ceiling wood panelling on the walls upstairs. That's not that weird, except that the panelling was designed to hide the door of the only bathroom up there. We found it by accident (the door didn't have a handle, it had a latch that you lifted up to open the door) and just about fell into the bathroom. That was a little weird...can you imagine have to feel along the walls for the door in the middle of the night? Then, when we went into the bedrooms, we thought it seemed oddly cold (we were looking in January). Opened one of the closets to see the roof beams! There was no insulation in either of the bedrooms up there! This is in Minnesota, where -20 degree Farenheit temps aren't unknown!
Third house had murals. Wallpaper murals that covered entire walls of the house. There was the forest mural in the living room, complete with animals looking out from behind trees and a small cabin with people chopping wood. On the wall across from this mural was a full-wall mirror, so the mural was repeated! Downstairs was the ocean mural, again covering a full wall, and again with a mirror on the other side to replicate it. Plus many of the walls were painted with forest or ocean motifs (bears, dolphins, etc) that were in bad shape (faded, peeling). I know that paint/wallpaper is not that hard to deal with, but the idea of having to remove huge swaths of wallpaper and repaint most of the house was too much for DH and I.