Picksaw

It is the first tool in the game that will cut Lihzahrd Brick. Until you have one, the Temple is somewhere you walk through rather than somewhere you can open up, and the whole structure stays exactly as generated. It doubles as an axe as well, so a Temple trip does not need a second tool taking up a slot.

The Spectre Pickaxe reaches further and the Shroomite Digging Claw digs faster, but neither one touches Temple brick, so this stays in the bag regardless. The speed gap matters less than the numbers imply: once mining speed gear and a decent modifier are in play, this hits the game's floor for how fast a block can come out anyway. Because of how that rounding lands, most of the good modifiers end up identical here, so do not burn a fortune at the Goblin Tinkerer chasing the best one.

Strip every Temple brick out of the world and Plantera picks up the drop instead, so it is not something a demolition project can lock you out of.