With a recent invoice payment, we received a handwritten thank you note insert from a client, (and we were still in the middle of the assignment).
At a board meeting, we were given an iced sugar cookie in the shape of a unicorn with appreciative words of how unique our services were to the exact needs of that board and foundation.
Another time, we received a crystal vase from an executive committee with sentiments of how we served as the vessel for their cause to flourish and how they hoped we would remember them by filling the vase with fresh flowers in the future.