I'm probably going to regret admitting it, but "In Which We Serve" (especially the stirring voice over at the end explaining how Britain is going to kick Hitler's butt over the footage of Formidable, or whichever carrier it was, ploughing through a head sea) is quite emotional. I'd be a patsy for propaganda.

In a bid not to seem entirely childish, here's another vote for Its a Wonderful Life, and yes, the end of Life is Beautiful, when the boy sees the American tank come round the corner and shouts "It's true"