The national flag of Nepal is the world's only national flag that is non-quadrilateral in shape. The flag is a simplified combination of two single pennons, the vexillological word for a pennant.

Are there any square flags?

Switzerland and the Vatican City are the only two countries with square flags.

Which state does not have a rectangle flag?

The chevron is azure containing a white and red "O" and 17 white stars. The Ohio Burgee is the official flag of the U.S. state of Ohio. It is a triangular swallowtail flag, the only non-rectangular U.S. state flag.