The most famous "last stand" in modern French military history is probably the Battle of Camerón, where 65 Foreign Legionnaires held an abandoned building against 3,000 Mexican soldiers for roughly 10 hours. The Legionnaires were whittled down to roughly 2 combat-effective soldiers at the time of their surrender, with the remainder killed or wounded. This was in 1868, which predates your timeframe by a significant margin, but again - it is the most famous.

I say that it is "the most famous" because the French have a storied military history littered with episodes equally as courageous - the Second World War is as rife with potential candidates for your question as any other era. The French divisions charged with protecting the Dunkirk evacuations fought themselves effectively to death covering the roads leading to the beachhead. The Free French fought with great distinction especially in Africa.

It would be helpful to answerers if you had more details to give; technically this doesn't break AskHistorians rules, as you are not asking for examples... but the vagueness of the particulars leads us down that path. Could you elaborate please?