Was stuck in the Paris train station at 5 AM at the end of a Eurail-pass trip. Needed to get a tram ticket to get to the airport in ~1 hr. Tickets cost €18 in coins, or a chip card; I had only paper money. After ½ hr of panicking, I found a shop that had just opened and I asked the shopkeep, while holding up a paper bill, what basic (and probably incorrect) French I remembered from high school:

"Avez-vous du coin?"

Caught the plane with 3 minutes to spare.