Two flags unmentioned that deserve attention:
Nepal is so bad-ass it’s the only country in the world to ignore convention, skip the rectangle and come up with a double pennant design. Is it because the wind blows so hard in the Himalayas that the reduced surface space works better? Or they ran out of cloth? Or is it the famous Nepalese humbleness (we don’t ask much, this will do just fine). Whatever, Nepal deserves mention for defying convention in the face of quadrilaterals. (The Swiss tried to offer up a square flag, but they caved to peer pressure for their national flag.)
The Le Tricolore of France is a thing of elegance, the simple vertical lines like many things from Paris a real fashion trendsetter (see cheap knockoffs from Italy, Mexico, Romania, Ireland, etc.). The boldness of red, white and blue still the best combination for a national flags of great nations — nods to you, Great Britain, USA, Liberia and Cuba (wait, what?). Of course each country applies unique symbolism to their nation’s colors. In France’s case the red symbolizing the blood spilled in revolution and war, the white for quickly surrendering when surrounded, and the blue for the period of ennui and regret after sacrificing either too much (see WWI, French Revolution, Napoleonic and colonial wars) or too little (WWII).