It's a struggle to pick a favorite Swap Shop vendor, considering the location's labyrinthine size. It's hard enough to see everything the place has to offer, let alone select the best from among the myriad booths filled with "I'm in Miami, Bitch" tourist towels, lingerie that you hope hasn't been worn, lingerie you know has been worn, knives, golden Our Lady of Guadalupe watches, and coconuts guaranteed to cure your hangover. (Yes, we bought one of each.) But what makes Dr. Sound stand apart? The fact that, after four years, the window tinting ($140) you bought for your new ride will still be bubble-free and like-new. That's the thing about some Swap Shop purchases: They're fun for a minute but fall apart by the time you get home. Not so with Dr. Sound. They guarantee their work, and they'll have your system and tints installed by the time you've finished that coconut.