Mine

The Mine and its variants explode when stepped on by any entity other than creepers, ocelots, and cats; the Furnace Mine only explodes when right-clicked on, and the Track Mine only explodes when any Minecart passes over it. All Mines have a radius of approximately 5 blocks. The default Mine cannot be placed underwater, and a submerged Track Mine will not destroy surrounding terrain when detonated.

Dirt Mine Recipe
Dirt can be replaced with Cobblestone, Diamond Ore, Furnace, Gravel, Sand, Stone, and Rail.

Usage
Right-clicking a Mine with Wire Cutters defuses it, thus allowing for it to be broken. Right-clicking a Mine with Flint and Steel re-enables it.