What is the rarest quarter in the world?

Can you tell me, what exactly is the rarest quarter in the world? Is it a specific year, mint mark, or design that makes it so rare? And what kind of value does it hold, both in monetary terms and as a collector's item? Is it something that a regular person might stumble upon in their change, or is it something that only serious collectors would be able to find and afford? I'm really curious to learn more about this rare and intriguing coin.