"Eternal Sunshine of the Spotless Mind" is a 2004 dark comedy about a couple in a dysfunctional relationship attempting a newfangled method of mind control to forget about the pain they've caused each other. Written by Charlie Kaufman and directed by Michel Gondry, the film boasts over 50 four-star reviews, as well as prominent ranking on several movie critic's lists of top films in the past decade, including #1 on Chris Sawin's favorite movies of the 2000's.
If you have not seen this movie, then Kay firmly believes that the best way to enjoy it is with minimal advanced knowledge of the plot itself (so the details above were written intentionally vague). The film has an all-star ensemble with Jim Carrey starring as Joel Barish and Kate Winslet portraying Clementine Kruczynski (his love interest) while Kirsten Dunst, Mark Ruffalo, Elijah Wood, and Tom Wilkinson round out the cast.
Kay once loaned the movie to Psycho Andy, but Andy returned it about 4-6 months later having still never seen it.