Until this morning mine would definitely have gone to "buying a metro ticket in Paris". I mean, who has ever actually had a conversation about this? You look at the map, buy tickets from a machine, and don't even have to bother interupting the flow of your iPod. However, this morning I found ratp's wonderful interactive site which helps you to plan metro journeys. Click on your departure station and then mark it with a green flag as your departure station. Then select your destination station and mark it with a red flag. You can also click on the local map symbol to plan your walking route to an attraction once you have finished you metro journey. It is a really user-friendly, practical tool which my Year 9 enjoyed experimenting with. It then isn't too difficult to slip in a quick "carnet-buying" conversation before the glow of the website wears off.
If you have any nominations for more tedious topic for MFL (or any other subject you teach) please drop a comment on to this post and we'll see what ideas and resources we can come up with.