The litwick family.
It may be old news but I still think it's probably the most disturbing.
Sucking out peoples souls and what not.
Pesky forum trolls
Feebas discussion? .3.
Anyway, I'd have to say the Ruins of Alph from Johto. That place gives me the creeps
Also the Altering Cave. Why is it shaped like Mew?
I actually think the Ruins of Alph is interesting with all of the history and puzzles. However, I'm not familiar with Altering Cave.
Credit goes to 00swms at Forever and Again
What is the altering cave?!?