I think my very favorite is the cream puff swan with ice cream and chocolate sauce at Les Chefs de France... phenomenal. My sons had the apple tart and the mint chocolate cake there as well and absolutely loved them.
The maple creme brûlée at Le Cellier is delicious as well.
Anything at Les Halles is great, too - the eclairs are yummy! Pair one of those with a lobster bisque and a baguette and that’s a fabulous meal.
And my 16 year old would be very mad at me if I didn’t mention his favorite of all time - the churros at the quick service in Mexico.