What is most unique coin you have?

I’m interested in coins that break away from the common rules/designs that most coins follow, wether it’s the material it’s made of, it’s shape, it’s face value, or something else. That’s what makes them unique. I want to know what is the most unique coins that you have.

A small value of several euros, but it's the last survivor

N#407391

And I'm looking for a cheap coin from Iran 1 Real ۶۵۳۶, for years, without success, so rare that even the Numista coin file wrongly quote it :)

Not exactly unique or rare (who knows how many survived to our time?), but the material - porcelain - makes it special:

N#17490

Dejan

…but the material - porcelain - makes it special

Sure they are quite interesting notgelds