A Lawn Mower.
The Lawn Mower can be purchased from Pitchfork Jeb's Farmer Supply. It is used for harvesting grain-type crops, like wheat, corn, and sugar cane. If used to harvest Root type crops, it will kill them. To place it, go to your farm, and left click on it. Select place. Simply walk over your crops while holding the Lawnmower and it will harvest your crops. The Lawnmower is faster than the Scythe, as it can harvest two rows at a time.