When in Paris, this is a must. I go for the macarons. I'll but a gift box to take home and a few to eat as I walk down Champs-Élysées.
Coco Chanel had a standing table here. It was where she got her chocolate fix. It's old and beautiful. They are famous for their Mont Blanc which is a meringue topped with whipped cream and covered in chestnut cream.
People go there for the breakfast - don't bother. Just indulge in their patisseries. You have to make a reservation for their Tea Room, but if you don't care for the ambience, you can always buy some treats at the counter and go across the street to the Jardin des Tuileries. Just watch put for the pigeons!