The Destruction Gadget allows you to destroy a massive amount of blocks at once. Blocks destroyed are not dropped, they are gone forever (though you can undo with U by default).

Sneak right click it to set the area it will effect. Set the number in each direction to say how many blocks in that direction it will break.

If you set it so that Up, Down, Left, and Right are each 1, it will break 1 block in each direction away from the centre breaking a 3x3 area.