Paulus Hector Mair, a 16th century German civil servant, left us a "fechtbuch", or fencing treatise, that included a section on exotic weaponry such as sickles, flails and scythes. Included are instruction on how to use the scythe as a weapon, and illustrations showing the techniques in action.
Here are a few pictures from the book.

So while I do not know if there are record of the scythe actually used as a weapon in earnest, its application as a weapon has at least been considered in the 16th century by an eccentric German, and techniques for fighting with a scythe was recorded.