No matter how cool your pair of shades is, we're sure there are times when you'd like to have a different lens to look through. Smith Optics Interlock Sunglasses ($140) use a unique system that allows you to turn the glasses' stems to "unlock" the lenses and switch them out with a different shade or color. In addition, they also feature an eight base lens curve for optical clarity, 100 percent UV protection, and come with two extra sets of lenses.