What is a word to describe one of kind person?

There isn't one perfect word to describe a one-of-a-kind person, as it can depend on what makes them unique. Here are some options, with different nuances:

For personality:

* Exceptional: Out of the ordinary, remarkable.

* Extraordinary: Outstanding, impressive.

* Unforgettable: Leaving a lasting impression.

* Irreplaceable: Unique and valuable.

* Original: Genuine, authentic, not imitative.

* Eccentric: Unusual, unconventional, quirky.

* Idiosyncratic: Having distinctive traits.

For positive qualities:

* Exceptional: Implies a high degree of excellence.

* Remarkable: Draws attention due to their specialness.

* Singular: Uniquely outstanding, often in a positive way.

For impact:

* Influential: Having a strong impact on others.

* Trailblazing: Pioneering, innovative.

* Visionary: Having a clear and unique perspective.

You could also use a phrase like:

* One in a million

* A diamond in the rough

* A rare gem

* A breath of fresh air

Ultimately, the best word or phrase depends on the specific qualities you want to highlight about the person.