The 1/2" and 9/16" and the occasional 3/4" are what I call planter wrenches.  Each year, during different maintenance tasks in the crop or hay field, I plant a few of these in hopes of having a bumper crop of replacements sprout forth.  Has yet to happen but doesn't keep me from trying again the next year.  If my wrenches ever do produce a crop, I'm going to retire from the income from selling those alongside my contracts for the marshmallows I grow and the unicorns I background.