Just 16 years in, it's been a banner century for gear. The biggest stories in consumer products have been about insurgencies — old tech being overtaken by new. Since 2001, the rise of legal music downloads has paved the way for an almost entirely digital media landscape, making CDs and DVDs little more than shinier updates on 8-track and VHS cassettes. Long-lasting, energy-efficient light-emitting diodes have moved from industrial applications into the home, finally unseating Thomas Edison's incandescent bulbs. Smartphones have replaced the laptop or desktop computer for many people, and touchscreens are pushing physical buttons toward design extinction. Innovations in lithium-ion batteries haven't done the same for internal combustion engines, but the end of the gas-burning automobile is clearly nigh.
And all of these trends can be traced back to specific, groundbreaking products — not proofs of concept or R&D contraptions (like Google's driverless car, for example), but real things that people actually bought. In picking out the most notable products of this century, we looked for gear that wasn't just the first example of a new kind of gadget, but the first to truly create or redefine its product category. Nearly every pick has been improved on or made obsolete by subsequent generations and opportunistic competitors. Still, this is the 21st-century gear that changed gear, and the world.