Gunpowder

Gunpowder, formerly known as Sulphur, is an item that can be obtained by killing Creepers, Ghasts or looting dungeon chests.

Uses
Gunpowder can be crafted into TNT and Fire Charges, and it can be brewed with any potion to make a Splash Potion. Fire Charges were added in minecraft 1.2.2, and has the same properties as flint and steel, except if launched from a dispenser.

Placing
Although it may have the look of Redstone, Gunpowder cannot be placed on the ground as a wire.

The items for fire charges can be put anywhere on the crafting grid.

History
In Indev, mob drops were randomized, so when a Pig was killed it could drop gunpowder instead of Pork (seen here).

In Beta 1.0, Gunpowder was renamed Sulphur, but reverted to its original term in Beta 1.3.

In Beta 1.9 pre-release 4, gunpowder was made usable in brewing to create Splash Potions.

Schießpulver Sulphur/es Poudre à canon Puskapor 화약 Buskruit Proch pt-br:Gunpowder Порох 火药