An absolute must-visit for myself on St. Denis, Arthur Quentin is an exquisitely sophisticated kitchen store for anyone into high quality food-ware and home chefdom and dining. Note that you can also find perfectly reasonable niche cooking utensils etc. along with the pricier things mentioned by the other reviewer.
Divided into three linked rooms, the first room is more of an eclectic melange of fabrics, objects, luggage etc. and also quite lovely. The other two are dedicated to cookware and flatware, tableware, glassware, respectively.
Friendly, helpful staff who always wrap everything beautifully for presents or otherwise. Equally lovely to browse at the collection of marvels and spend nothing at all.
Note that it's the companion store to Bleu Nuit across the street. Also worth a visit for those into linens, bedding and things of the night.