Musket

Breaking a Shadow Orb hands you this along with a supply of ammunition, and in a Corruption world it is usually the first real firearm you own. The pairing matters: without that free ammo the gun would be awkward to feed at that point in a run.

Slow and heavy. Each shot lands hard enough that a miss stings, and it no longer autofires, so you are clicking deliberately instead of holding the button down. That suits it. The built-in critical rate is far above what a gun normally gets, so patient aiming pays better here than with anything else available this early.

Eaters of Souls and the other slow Corruption wanderers fold to a single shot each, which lets you clear a chasm without burning a stack of bullets. It struggles the moment something fast gets on top of you, and that is the argument for the Crimson equivalent, which trades punch for rate of fire.

The tooltip lifts a line from a Stavesacre song. The sprite has drifted a long way from an actual musket over the years and now reads closer to a blunderbuss, which is arguably more honest given how quickly it reloads compared to the real thing.