The gold ring
This scam happens a lot in France especially in big cities like Paris. Usually, near a tourist attraction, one woman will start to talk with you and ask you if a gold ring that she found is yours. You reply no and she will ask you if you want to give it to your wife or girlfriend. If you accept she will ask you money to eat and you will feel forced to give her. Guess what the ring is not even gold. Usually is brass and have a value next to zero euros. So make sure you don't accept anything and just ignore her. She will go away. If you engage with her on this deal she will not leave you alone and ask you money.