Wood

Wood is a byproduct of trees. It is mostly made up of water, cellulose and lignin. Water and cellulose are the soft squidgy bits, whilst lignin is the hard bit. If you hit a tree whilst in possession of a reasonable amount of kinetic energy, it is the lignin that causes the injury, not the water or the cellulose.

Wood is very useful, as it is combustible, good for construction and comparing relative displacement in witch trials.