TNT

TNT acts like a normal block in Creative. However, in Survival it behaves like the Creeper's explosion. Upon being struck by the player, it will start smoking and flashing white. If there are no blocks to hold up the TNT block, activating it will make it affected by gravity and it will fall. After a few seconds, it explodes, destroying a vast amount of blocks, mobs that are nearby, and even the player if they are not careful. Hitting it a second time in survival will stop the countdown and make it so you can pick it up to use later. TNT can clear water and lava. Setting TNT on fire causes it to explode. However, if the TNT falls in water, the explosion will not destroy any blocks at all but still cause damage to the player.

TNT will damage surrounding blocks depending on what blocks are directly touching it or not. Empty space will create a larger destructive radius, while a TNT block completely surrounded by rock will destroy an exact 3x3x3 cube from it's center. Obsidian doesn't have a set area affected by explosions. The resulting hole will not follow a certain pattern and strange effects are caused by enclosed Obsidian explosions.

This trick can be abused to mine out long 3x3x3 hallways without using your valuable pickaxe charges.

Since the Redstone update, TNT monster traps can now be created and used successfully, making TNT a valuable resource and a powerful defense. When exposed to a current, the TNT activates as if it had been activated by a player. Combine this with a pressure plate and you can create an automatic defense for your buildings (although a one-time-use, as the TNT needs to be replaced).