Answer: Nepal

It isn’t the coloration or the symbolism thereon that makes the Nepalese flag truly unique among the world’s national flags; it’s the shape. Unlike every other national flag on Earth, the Nepalese flag eschews the traditional rectangular shape and is instead in the shape of two conjoined pennons (short triangular flags, not to be confused with the long and billowing pennants popular among royalty and militaries in the Middle Ages).

The design, officially adopted with the formation of the constitutional government in 1962, wasn’t selected on a whim. For centuries the Nepalese people had used two individual pennons to represent the region. Those two pennants had been merged into a unified flag in the 19th century and upon the adoption of the constitution in the 20th century, the construction of the flag was formalized (the constitution itself has specific guidelines including precise ratios for each triangle).

The flag’s shape is intended to call to mind the peaks of the Himalaya mountains that cradle the country, the blue border symbolizes the long periods of peace and the stability of the border that the Nepalese people have been blessed with, and the white icons representing the crescent moon and sun represent the desire of the people to see their culture and country last as long as the celestial icons that adorn their flag.