Shutter Island
Having never seen this movie before, I had gathered less from a spoiler and more of a pop culture osmosis that there was a big twist ending. I really loved the confluence of knowing about the twist, but not knowing what it was. I felt like a detective along with the main character, trying to solve the real mystery. I likes the elements of "amateur" writing and bad CGI there were so obvious yet made sense upon reflection.
I also enjoyed the rivalry of psychology vs. psychiatry that played out.
This movie has some obvious similarities to Inception, I enjoyed talking about fan theories that relate the two with my friends whilst on a spooky lake house trip.