In France, if it's at a vide-grenier,* brocante,** or marché aux puces*** it's quite common to haggle. And you don't need much language to do it. If you're looking at something that's being offered for 25 €, you can look it over, then look the vendor in the eye and say "15?" You'll probably get it for 15 or 20.
It's not uncommon for a vendor to saunter over while you're looking at something and offer a discount without being asked. My wife and I were at a vide-grenier this last weekend and picked up a pigeon lamp, converted to electricity, for 8 €. The vendor had it marked at 15 € but offered it for 10 with no prompting. The drop to 8 came just by looking at him and asking "Huit, monsieur?".
*Vide-grenier -- literally, empty the attic; kind of like a big garage sale with many dozens up to a hundred or more tables where private citizens and some professionals sell their stuff. Quite common spring through fall throughout France.
**Brocante -- a business in a fixed location where the owner is a professional who buys old items, fixes them up if necessary, and offers them for re-sale.
***Marché aux puces -- a flea market with vendors, generally professionals, who temporarily set up along a street or other designated location, often on a fixed schedule.
And if you're curious, a pigeon lamp is a type of gasoline-fueled lamp that was widely sold in the pre-electricity days in France.