It's thought the measure of a passport's power is the number of countries it allows its holder to travel to without applying for a visa.
Based on this, German passports - held by millions - have the most clout, allowing their citizens to go to a total of 176 countries out of 218, visa-free.
While millions don't hold a passport for the Sovereign Military Order of Malta, it is precisely their rarity which makes them so special.
Only three are issued at any one time.
These go to the three highest officers in the Catholic order: the grand master, deputy grand master, and chancellor.
So what is the medieval order?
Its full name reads the 'Sovereign Military Hospitaller Order of Saint John of Jerusalem of Rhodes and of Malta.'
It originated as the Crusader Knights Hospitaller in 1099, reports Business Insider .
Every other officer of the order have to use the passports issued by their home countries.
Interestingly, the military sovereign doesn't have any of its own land.
It lost the island of Malta in 1800 and since then it's "land" has comprised of two extraterritorial properties in Rome, from where it issues its own postage stamps, currency, and passports.
Nowadays, the order operates as a medical charity which provides medical assistant and relief all over the world.
It's believed to count 13,500 knights, dames, and chaplains along with 80,000 permanent volunteers and 25,000 employees among its members.
While the UK accepts hundreds of passports, the order's is not one of them sadly.