I found a nice patch of Equisetum in one of my walks the other day.
This plant is commonly found along the banks of waterways. I think this is a really cool plant because it was one of the first I remember learning about when I took botany in college. I came across a nice patch of these plants shortly after I was introduced to them. The genus is an ancient one and is the last survivor of the class Sphenopsida. These either are the first or among the first vascular plants. This class of plants were once among the most common and abundant plants on earth. This was prior to the emergence and evolution of the angiosperms.
Oil and coal that we use today is the product of plant material that includes plants from the Sphenopsida. During its heyday there were species from this class that grew as tall trees.
You can find out more about these plants and their history here.