Lucky Coin

It only drops during a Pirate Invasion, and from ordinary pirates the odds are thin enough that you should not plan around it. The Pirate Captain is better. The Flying Dutchman is far better than either, so the sensible approach is to farm the ship rather than the crew.

That setup is specific. Push the invasion past the halfway mark, then get airborne on a small platform or a flying mount, high enough that ground spawns cannot reach you but still low enough that they keep cycling and respawning. What is left able to reach you is Dutchmen and Parrots. Parrots are harmless and do not count toward the invasion bar, so you can kill them freely without ending the event you are farming. The same trip also produces the Discount Card and the Gold Ring, which is the real reason to do it properly rather than grinding regular pirates.

In Celebration and Zenith worlds you can skip all of that, because the Princess stocks it once an invasion has been beaten.

The bonus coins roll whenever you damage something, and the roll ignores how hard you hit. That flips the usual logic completely. The best farming weapon you own is the weakest and fastest one, and a terrible modifier on it is an upgrade rather than a problem. A minion chipping in for a single point against something with a large health pool pays out far more than a weapon that kills the same target in two swings.

There is a ceiling built into that. Every enemy can only pay as many times as you can land hits on it, so the total you can squeeze out is set by how many hits its health bar allows. High defense targets like Mimics are ideal for exactly that reason: they blunt your damage down to the floor and stretch the hit count out.

A Slime Staff carrying the worst modifier you can find it in, worn with summoner armor that raises the minion cap, is the well worn answer. The baby slimes attack constantly, each hit lands for almost nothing, and every one of those hits is a separate roll. Any fast firing weapon works on the same principle if you would rather shoot, so a Minishark or a chaingun does the job.

For targets, invasions and Solar Eclipses give you the density. The altar chamber in the Jungle Temple is a quieter and steadier stream, with the occasional Mimic wandering in to inflate the take. A slow, high health boss you can safely stand next to, the Wall of Flesh being the usual pick, works surprisingly well for the same reason Mimics do.

Enemy health goes up, and since your income is measured in hits landed, the payout climbs with it. The catch is that enemies in Expert and above will pick your coins back up off the ground after a short delay. Anything that wanders off screen or escapes with money in its pocket keeps it. Fight in a closed arena, do not let stragglers leave, and sweep the floor before you move on.

• Damage bounced back at an attacker, from Turtle armor or a Thorns Potion, earns nothing at all.
• Traps you wired up count in single player and stop counting in multiplayer.
• Statue spawned enemies have been excluded for years, so the old dart trap and statue farm produces nothing extra.

It also nudges your luck upward while equipped, which quietly improves unrelated drops in the background. And because it can roll the Lucky modifier, it is possible to end up carrying an accessory whose name says lucky twice. Later it folds into the Coin Ring, which keeps the effect and adds a coin magnet, so the slot is not stuck with it forever.