a one of a kind opportunity
This expression can be used in a literal or figurative sense. A work of art, for example, could be completely unique, which would literally make it one of a kind. On the other hand, you may regard somebody you know to be so special and different that you endearingly, and figuratively, refer to them as 'one of a kind.' It is commonly used in both a social and professional context. In the former, generally speaking, to discuss people, and in the latter to discuss marketing and opportunities.