Full Metal Jacket. Good stuff. I love how the first and second half have storytelling parallels, but with very different cinematographic styles. Tighter, controlled, fortifying training scenes vs. the looser, edgier feel in Vietnam. Apocalypse Now is definitely the better Vietnam film, though. It’s been quite a while since I last saw Platoon or The Deer Hunter. Vincent D’Onofrio was also awesome in Mystic Pizza.
My updated Kubrick leaderboard: