Your favorite psychological thriller and/or horror?
I've only watched one psychological thriller in recent history: Inception. I liked it although it seemed a bit confusing and dragged on a bit.
I played a psychological horror visual novel: Doki Doki Literature Club. Pretty good although I have yet to finish the whole thing.
I also like stuff like Twilight Zone, if that counts.
Edit: Oh, I forgot Mulholland Drive as a thriller I watched. Great movie.