Umbrella

Drifting down with it open is slow and dull. Just fall normally and flick to it in the last moment before you land. The damage cancels instantly. That turns a chest hunting trip into free vertical travel: dig straight down, drop, tap the umbrella at the bottom, keep going.

The best use has nothing to do with falling straight. Build a track that ends in midair, get to top speed, ride off the end and open it. You keep almost all of your horizontal momentum while barely losing height, and from a high enough rail one launch crosses an absurd share of the world. It is the cheapest long distance travel you can put together before wings.

It counts as a shortsword, so you can hit things on the way down, though every swing drops you for its duration. A dash accessory covers that gap neatly, since the dash lands hits without interrupting the float. Do not expect much from the damage itself.

Surface chests hand these out often enough that most players never pay for one. If you missed it, the Skeleton Merchant carries one, but only on the right moon phase, so it is a wait rather than a purchase you can schedule.