I've seen the whole range of bikes in the rack at work. Old mountain bikes, road bikes, newer big box store bikes, comfort bikes, a few IGH hybrids like mine, regular hybrids, a triathlon/time trial bike that gets ridden with flip-flops and basketball shorts... and yes, a few years ago there was a unicycle. Which was showboating. If ever there was a machine that you could take inside and tuck under your desk, a unicycle would be it.
Of all of these, I suppose the time trial bike is the least commute-worthy, but it works for the guy who rides it. He used to do triathlons, had the bike, and decided it would do as well as any other for pedalling to work on.