Tyler Cowan at Marginal Revolution blogs on a study of the best and worst flags in the world.
The top flag is Gambia with an A+ 90/100. New Zealand gets a C and 55/100.
One of the bottom flags is Mozambique, with a D- 37/100.
Yes they actually have an AK47 on their national flag!
The very bottom score with an F 2/100 is the Northern Mariana Islands.
He notes it looks like it was constructed from clip art. Indeed it is horrible.