The Banana Sword is a hidden weapon in Cube Life: Island Survival.
The banana sword was added in Version 1.1, although at the time there was no documentation to confirm its existence and it could not be found in the Crafting Guide. It returned in Version 1.5 with an updated sprite. Still, there was no mention of it anywhere until Version 1.6, which added the recipe database to the Inventory. Though it still may not be found in the Survival Guide, selecting either a banana or a stick while the inventory is open will reveal it as an object that may be crafted.