@olynch more of a recommendation on what not to do, but our whole group regretted wasting a day visiting Versailles. It's fine, but there were things in the city we didn't have time for that we collectively agreed would have been time better spent.
Also, croissants, pain du chocolate and macarons seem to get all the love in tourist sites, but if I can only get one item from a French bakery, it's a kouign-amann (pronounced queen aman). Highly recommend you get one while you're there.