Sure, having a German passport would be great. I mean you'd be able to visit 177 countries around the world without needing a visa. But life is about more than quantity, it's about rarity, and the rarest passport of them all would have to be of the Sovereign Military Order of Malta.
For those of you who don't know what that is, the Order of Malta is a Roman Catholic institution or order which goes by the motto of "Defence of the (Catholic) faith and assistance to the poor." It is active in 120 countries, where it helps to care for people in need through its medical, social, and humanitarian efforts.
This order is home to the rarest passport in the world, with only 500 of them in circulation around the globe right now. This is, quite literally, the most exclusive passport in the world. According to the Sovereign Order of Malta, diplomatic passports are only granted to "the members of the Sovereign Council (the government), to heads and members of its Diplomatic Missions (as well as their consort and minor children), and – with very few exceptions – to senior figures in charge of a special missions within the Order of Malta."
These passports are strictly linked to the duration of a given assignment by the Order, and thereby only remain active for 4 years. The Order continues diplomatic relations with 106 states, so all of these states accept these passports as a valid form of identification. As of now, the order is made up of over 13,500 knights, dames, and chaplains along with 80,000 permanent volunteers and 25,000 employees, meaning it's a tough chip to score even if you're inside the system