Master-piece

An invidious, malicious song, replete with the sharpest terms, is, according to them, the master-piece of human wit.

Source: wiktionary

...She is romantic—clever—needs excitement; and, therefore, flavours her affection with a handsome seasoning of remorse. I shall expect a master-piece from you to-night; till then adieu, and pray feel as much at home with me as I do with you. By the by," added he, turning back from the door, "be sure you fill the paper; women judge of the strength of your attachment by the length of your letters!"

Source: wiktionary