The Scythe is a tool in Stardew Valley and is also a weapon. It deals low damage to monsters. It is one of five tools that the player starts with when starting a new game. Like the rest of your starter tools, you cannot sell the Scythe.
The Scythe, unlike the other 4 tools, is the only tool you cannot upgrade. But is the only tool (besides a weapon) which doesn't use up energy to use/swing.