I think one of the best places in Paris for oysters is this little bar in Saint-Germain.
We recently went to Huitrerie Régis for lunch with our friend Katrina. It was a warm, sunny fall day, so we sat outside on the terrace and ordered a bottle or two of crisp white wine and a giant platter of oysters, clams, and crevettes (shrimp). It was the perfect Parisian lunch, with a side of plenty of people watching.