Money Trough

Using it hangs a floating piggy bank in the air where you are standing. It does not follow you the way a pet does and it cannot go in the pet slot; it parks where it was summoned and stays there until it fades a few minutes later. Calling another costs nothing, so treat the timer as a non-issue rather than a resource. In multiplayer anyone can walk up and open it, and each person sees their own storage inside. It also counts as your wallet at a shop: if your inventory is short on coins, the vendor takes the difference out of the bank.

The obvious source is Blood Zombies and Dripplers on a Blood Moon, and those odds are grim. The better plan is to fish through the same Blood Moon, since Wandering Eye Fish and Zombie Mermen come up on the hook and give it up far more readily than anything you kill on foot. Statue-spawned versions of the land enemies technically drop it, at odds bad enough to ignore, so a statue farm is not the shortcut here. Blood Moons have no fixed spawn rate, so keep a Water Candle down and a Battle Potion running while you sit at the water.

Dying costs you a share of your coins in Classic, most of them in Expert and every last one in Master, so being able to deposit the moment a fight turns is worth more than an accessory slot in the harder modes. With a little preparation a single Blood Moon can produce one. Waiting until after the Wall of Flesh works against you: the Hardmode Blood Moon roster is much wider, the two enemies you want make up a smaller share of what spawns, and the same drop gets noticeably harder to land.

You can put the Money Trough itself inside the flying bank it summoned. When that despawns the trough is sealed in there and you need a real placed Piggy Bank, or a second trough, to get it out again. Mark it as a favorite and the game refuses to store it, which takes two seconds and removes the problem permanently.

Fishing gear, hammers, spare armor sets and situational potions can all live in there and stay reachable from anywhere in the world. For most players that is the real reason to carry one, ahead of the coin protection.