Fixed gear proponents enthuse about the simplicity of fixed gear bikes -- because there are fewer moving parts, the bikes are cheaper, simpler to maintain, and bulletproof.
In reality, though, we ride the bikes because they're so cool. Now that everybody has gotten into fixed gear hipness, though, they're not as hip. They're as ubiquitous as dog droppings on Paris sidewalks. For the ultimate in simplicity, can I propose the Nimbus Ultimate Wheel unicycle? This is literally just a wheel with two pedals. No gears, no brakes, no extra wheel, no pesky steering tube, no bottom bracket or cranks, no chain or chainring, no rear cog, not even a seat. Its compact size even makes it transit friendly for multimodal use! And because it's so difficult to ride -- even moreso than a standard unicycle -- nobody but the truly hip will ever ride this wheel.
Props to my Colorado friend Paul, who pointed me to unclutter.com.