You can spend money in almost any way imaginable in Las Vegas, but the best way to actually leave with what you paid for is to go shopping. We consider it one of your better options in terms of having something to show for your empty wallet.
If your tastes run to the expensive, you will want to schedule in some serious time at the luxury shops of Crystals and Via Bellagio. They are even within walking distance of each other if you're not wearing heels. Also, you may be surprised to hear that there are six certified Rolex dealers on the Strip alone, and that you can buy a Ferrari or Maserati direct from the showroom at the Wynn. If these are a little (or a lot) too pricey for you, check out Fashion Show mall at the north end of the Strip, Miracle Mile Shops at Planet Hollywood Resort & Casino and The Forum Shops at Caesars. Tivoli Village and Town Square are outdoor walking malls with shops ranging from the cheap and chintzy to the pricey and tailored.
For charming little shops paired with a Vegas-only experience to match, head off the Strip to the Downtown Container Park, which is a gem of the city's downtown revitalization project. It's made from up-cycled shipping containers, and is home to lots of hip, artsy boutiques, galleries, restaurants, live music and even a play area for kids.
Since your trip to Vegas might not be as complete or as fun without a pilgrimage to an adult toy or superstore (whose wouldn't?), there are about 50 of them scattered throughout the city.
If you're looking for something specific, from a fast car to a fetish device, chances are, you can find it in Las Vegas.