Shopping in Mazatlan can be very predictable, with the usual trinkets and trash sold in store after store in the Golden Zone.  Not that there is anything wrong with that, of course!  But if you're looking for something a little different to take home as a momento of your trip, there are some better options:

The Copper Gallery-- located in the Golden Zone amongst all the other tourist shops, but offering beautifully crafted, handmade copper art.  From bowls to vases to sinks, all of these goods are made by artisans from Santa Clara del Cobre -- a colonial town in the mountains.  

There is a store selling natural cotton clothing nearby on the same side of the street, really gorgeous dresses for women and dress shirts for men!

Shopping for Necessities:

Gigante is the supermarket and is a great place to go if you need to stock up on supplies.  There are a lot of drugstores and convenience stores to pick up a bottle of water or small items, too.  The busses that circulate to Gigante are easy to find and are labelled "Gigante". Also can take a taxi or pulmonia.

There is a mall located near Gigante - a good place to go if you lose your luggage or need things like underwear and socks, or books (some English books available) or non-beach type clothing.  Any taxi or pulmonia can take you there, or there are many local busses that circulate past the mall. 

Sam's club is located near the mall.  If you are a member you can stock up on supplies there.