Wooden Boomerang

On the way out it hits once and keeps going. Once it runs out of momentum and starts turning around, it stops caring about how many enemies it has touched and begins cutting through solid ground. Position so that the target sits near the far end of the arc and a single throw can land several times, and you can clip things standing just inside a wall. Water drags it short. Melee speed bonuses push it further.

The Enchanted Boomerang is cheap to put together and strictly better, so this is a stopgap for the first hour of a world. If you find several in surface chests, the upgrade is also worth more than the parts that go into it, which makes it a quiet way to pad your coin purse early.

Wooden chests on the surface and in the upper caves, or from the Skeleton Merchant when the moon is full. Oddly, wooden crates never contain one, even though most of the other rare chest items can come out of them.