I've always been a fan of Zeitgeist but they've opened a second location, only a few doors down, that showcases items that I thought I'd never see in Colorado. The new space is almost three times the size of Zeitgeist and has all the usuals like Kartell and Herman Miller but also great new and classic designs from around the world. Parking can be tough but it is well worth the visit. The new shop is called zmodern as is the website.
Pros: Variety, Unique, Wide Price Range
Cons: Sometimes Parking