An awesome home-grown store is G.O.D. ( goods of desire), everything is Hong Kong themed, and the designers like to add some tongue-in-cheek to their items. For example, the Delay No More line is a joke amongst locals because the name sounds like a vulgar curse word in Cantonese.
For stationary and home-ware lovers, go to MUJI and UNIQLO in Causeway Bay or Kowloon. The Japanese brand is well known for practical, well-made and inexpensive things. They also have some nice snacks!
For serious Hong Kong style shopping, go to Island Beverly in Causeway Bay. (Causeway Plaza is worth a visit as well) The mall is full of tiny, tiny stores with funky clothing, jewelry and knick-knacks. Warning: claustrophobic people should especially avoid this area.
Lastly, for some touristy souvenirs go to Jade Market in Kowloon for Chinese jewelry, just make sure to bargain. For fake bags and other goods, go to the Ladies Market in Mongkok.
For some nice views of the South China Sea and some bargaining among the throngs of tourists in Stanley Market.