Sipperly laughed wheezily, then he saw that Janson was serious. An avaricious look crept over his fleshy features. “Well, joking aside, I’m really very fond of that dog,” he recovered. “He’s truly one-of-a-kind. Excellent guard dog … “
Robert Ludlum, The Janson Directive, 2002.
one-of-a-kind adjective [before noun]
used to describe a product or service that is the only one of its type, or that is very unusual:
The one-of-a-kind pieces are due to go to auction later this month. [Cambridge Business English Dictionary]