Empty Square Sacs

Sacrifices on empty squares are not as common as other kinds of sacrifices, but they can be just as deadly. Take this game, for example. Kalegin, playing white, decides to sacrifice a rook on the 20th move on an empty square. After it is captured, he begins an attack on his opponent's uncastled king. He then gives up a knight, also on an empty square, and is able to close in for mate a few moves later.

As you view this game, note how black is punished for neglecting to develop his pieces.