All the youtube links are expired... I always weep at Casablanca's Marseillaise, because my Mom, a Holocaust survivor, always wept at that scene.

Dancer beat me to Harold and Maude.

And there is another John Wayne movie where the Irish troops sing Down By The Glenside to their commander. It *might* be the same one where they sing to Maureen O'Hara... but that scene was actually in a Lucky Luke (French comic strip set in the Ancient West), where they sing to the commander.

And every single intro song to the bad guys in the new Suicide Squad was marvelous and wonderfully cast, if you will.