>>53802831Old Chateau because of ghost sightings.
Strange House is a close second.
Even though I'm a genwunner, the odd and unsettling places got better over the years.
>Pokémon Tower>Power Plant (gen 1)>Pokémon Mansion>New Mauville (gen 3)>Sendoff Spring (this one is a third place contender since it's inaccessible until post-game)>N's Roomand this is ignoring the unusual soundtracks played in these areas.