In the satiric sense, a charade, a mockery, an empty or absurd pretense.

Pièce de résistance

An accomplishment which is worthy of display and admiration:

English Wikipedia's 1,000,000th qualified article, Jordanhill railway station, was called a "showpiece of parallel collaboration." [1]

An outstanding example of a type:

Beacon Hill Park in Victoria, British Columbia is considered a showpiece garden. [2]

At environmentally focused Green Mountain College, the organic garden with its many Heirloom plantings is a campus showpiece. [3]

A performance which provides an opportunity for the display of a particular skill:

Luciano Berio's Sequenza XII is a showpiece composition for bassoon.

The Dying Swan was ballerina Anna Pavlova's showpiece.

A work of art or theatrical production presented for exhibition:

In 1994, Choreographer Jerome Robbins created a showpiece for the School of American Ballet based on composer Johan Sebastian Bach's Two and Three Part Inventions. [4]