Grate

Water, lava and honey fall straight through it while you walk across the top. That makes it a floor and a drain at the same time, which is the whole point of the thing. Wire it up and it flips to a solid opaque block, and any liquid caught mid flow gets held above it until you open it again or pull the liquid out with a sponge or a bucket.

Stand on a grate ceiling while you mine Hellstone and the lava released by the ore drains away underneath you, leaving the ore sitting where you can safely pick it up. No lava pooling around your feet, and no potion needed to do it.

Fishing near grates will disappoint you. The game counts them as solid when it measures how large your pool of water is, so a lake floored with them fishes as though it were far shallower than it looks.

The tooltip is a cereal mascot catchphrase, made to work by grate and great sounding identical.