DropCSS
An exceptionally fast, thorough and tiny unused-CSS cleaner
..., body and tbody to be implied/omitted, DropCSS makes no such assumptions; selectors will only be retained for tags that can be parsed from provided markup. It's also a good idea to run your CSS through a structural optimizer like clean-CSS, csso, cssnano or crass to re-group selectors, merge redundant rules, etc. It probably makes sense to do this after DropCSS, which can leave redundant blocks.