Corrupt Crate

Every one of these opens with a guaranteed orb reward inside. That matters because the normal way to get those is smashing orbs down in the chasms with a hammer, and each one you break drops a meteorite somewhere in the world and drags you toward a forced boss fight after the third. Fishing gives you the same weapons with none of that pressure on the world state.

The Musket is the one that starts a gun build years before the Arms Dealer would otherwise be useful. The Vilethorn pierces through walls and is the reason some players clear the early Dungeon faster than they should be able to. Mages want the Band of Starpower. The Shadow Orb light pet is the quiet pick, since a permanent light source that follows you changes how caving feels.

Everything else in the pool is material you would have collected anyway: ore, bars, coins, common potions and bait.

There is no reason to hoard them into Hardmode. The table is locked to pre-Hardmode loot no matter when you crack them, so holding a stack only delays the weapon you wanted. Open in bulk rather than one at a time if you care about the potion slot, because a run of Spelunker and Hunter potions turns one mining trip into a good one.