I just got back from a fantastic weekend in Paris. Saturday night went to Le Villaret. It was DELICIOUS. Really cute place, we had the tasting menu for 50 euros, though in retrospect wish one of us had splurged for the 70 euro tasting menu. I wasn't sure what wine to pick so we asked the owner/manager for help and he brought over a delicious bottle for under our price range.
Sunday night we went to the Relais de L'Entrocote. There are two of them in Paris and only serve salad to start, followed by steak frites. The only question they ask is how you want your steak cooked. Some people have claimed that it's all you can eat, but it's not. You get two servings of steak and frites and that's it. Really good, really fun place.
Monday night we went to Le Beurre Noisette. It was out of the way, in the 15th arrondisment, but really cute (tiny place) and delicious. They only had a set menu for Valentine's day, but it was all fantastic.
Highly recommend all three spots!