Bucket
necessary when creating fields for wheat, piece of lakes and canals, casting patterns of obsidian. Allows you to scoop up one block of lava or water source, and get cow`s milk.
If the player is swimming under water and scooping up empty bucket of water you for a moment, will create air space, which is enough to fill "light" player that contributes to an unlimited stay under water. To recover the bucket, just pour the water.
Kraft buckets of iron, as they can be found in the treasures. The probability of finding a bucket in a box treasure is 80%.