While The Half-Blood Prince may have one of the dullest color palettes in cinema history, the same usually isn't said for the story itself. While the sixth installment definitely struggles a bit as a book adaptation, the movie still stands as a high point chock-full of some of Harry Potter's most memorable moments.
Rest In Peace, Albus Dumbledore.
Between blossoming romances, mysterious horcruxes, missing memories, and finally some backstory to Lord Voldemort during his Tom Riddle years, Half-Blood Prince certainly has a lot going on. Throw in subplots about Draco & the Vanishing Cabinet, Dumbledore's private lessons with Harry, and, oh yeah, the whole Half-Blood Prince thing, and you've got a classic J.K. Rowling story branching in so many directions the author herself probably couldn't keep name them all today. But can you, right now?