I’m trying to identity one of a couple of grassy plants that grows throughout my lawn. This one looks like a sand burr, but doesn't seem to dry out and get prickly like those do. I live about 40 miles from the South Carolina coast.
The plant piece in your photo is from a member of the "sedge" family (Cyperaceae). The plant is of unknown type/species/variety. It might be what is commonly called a "nutsedge", and is considered a difficult to eradicate weed. Sedges comprise a very large, grass-like, plant family, usually (but not always) characterized by their triangular stems (in cross section). There are far too many genera/species to identify the exact type(s) that you have at your South Carolina location. I have provided a few informative links below.