I came across this page which showed the percentage of Chrome page loads that use various CSS properties. Unsurprisingly, width, padding, height, and display were at the top of the list, with over 91% of page loads having at least one occurrence of each property. This turned out to be a great learning opportunity as I went down the list and found properties I didn't know about before. A number of properties that were popular were ones that I didn't use regularly.
The takeaway isn't too clear, since popularity of a property might correlate with utility, best practices, design trends, or even poor but common practices. However, this list left me with a lot to learn: I haven't regularly used line-height, border-collapse, text-overflow, direction, webkit-font-smoothing, pointer-events, background-clip, word-break, text-rendering...the list goes on.
Small aside for some buttons made while fooling around at work