The end of Zulu, where the British soldiers sing "Men of Harlech" to counter the singing of the Zulu warriors. Or any time singing or volley fire appears.
In Zulu, toward the end, there is a lull in the battle. During that time the Welsh and the Zulus sing the war songs of their respective cultures. Depending on how you see it, this is either a moment of primordial kinship (sort of "All warriors are brothers") or the most badass thing ever to happen in Welsh history.
Hell, why not both?
Pretty much everything Color Sgt. Bourne does or says. "Alright then, nobody told you to stop working!"
