[Mark Hone]

My votes: Patton, Longest Day, Battle of Britain, Das Boot and The Cruel Sea. The Cruel Sea provides a fascinating counterpoint to Das Boot. Das Boot even has a scene which echoes (perhaps deliberately) the terrible moment when Jack Hawkins depth-charges the sailors in the water because there may be a U-Boat underneath.
I don't like Bridge On The River Kwai, primarily because it presents a story which is not a patch on the real one which inspired it, that of Colonel Toosey, who acquired a moral ascendancy over his captors such that one converted to Christianity after the war and wrote to him for forgiveness. It's an amazing tale which is well told in a Timewatch documentary which is sometimes repeated on UK TV History etc. Also the elite commando group spend much of their time moving through the hills on the skyline, as my old dad, a Burma veteran never tired of pointing out.