Iron Crate

Any water at any depth in any biome produces these, so there is no arena to build and no location to travel to. Fishing power is the only lever you have. A decent rod, real bait instead of whatever grub you scraped off a rock, and a Crate Potion do far more for your results than choosing where to stand.

The Falcon Blade is the headline. It swings fast, hits well above what you should have access to while still fishing in pre-Hardmode, and it exists in exactly two places: this crate and Mythril Crate. The Beguiling Lyre and the Ginger Beard share that restriction, though neither is a reason to cast. Underneath them sit Sailfish Boots and Tsunami in a Bottle, and the odds on that whole group are better here than on the wooden tier, so early fishing aimed at movement is worth pushing your fishing power for.

The loot table splits ore and bars into two rows, which reads as though you could get both. You cannot. One roll decides whether you get raw ore or refined bars, never a mix. More usefully, the crate refuses to come back empty: if the first pass produces nothing from the main groups it rerolls until something lands, so the real chance on every line above is noticeably better than the printed one.

Saving a stack to open after the Wall of Flesh used to be worth doing. It is not anymore. The crate is locked to its own tier and will not produce Hardmode loot no matter when you crack it, so the only reason to sit on a pile is inventory space. Open them as you catch them and you at least get the bars in time to use them.