I like Pet Valu (or "Pet Valloo", as my friend calls it) because, unlike a couple of well known chains in the city, they don't sell animals. (Before buying an animal from a pet store, Google that store's name, plus the word "cruelty" or "abuse".)
They also always have the brand of raw food we feed our dog. The staff is friendly, and even though the store isn't cavernous, they have a good selection of anything you might need for your pet.