Undoubtedly the best instrument ever created by mankind. The piano is not only able to play soft and loud, but it can also play multiple parts simultaneously, making a single pianist the equivalent to an entire orchestra. The piano marks the pinnacle of human music technology, which is ironic (but should not be surprising) because it was invented in the 18th century.
Should not be confused with a keyboard, a piano-imitating instrument which has poorer quality sounds and wastes electricity, an insult to the piano. Obviously for these reasons it is used in rock bands.
Sounds produced by any decent piano player can match the grandeur of an entire orchestra! Human technology has come far.