FlagWaver Pro

FlagWaver Pro gives you the world's flags in motion, waving on your screen. 
It does this using a fantastic collection of high-resolution flags from top flag expert (the long word for that is "vexillologist") Graham Bartram. 

This Pro version for the Mac includes as-standard all the flags from the extra flag packs that are in-app-purchases in the iOS version.

The app understands multitouch gestures on the trackpad, so it's easy to rotate and zoom the flag as it moves. You can even drag the cloth of the flag while it ripples in the wind, or open the settings window and change the wind-speed and gravity, live. 

It has an amazing collection of high-quality flags, including national flags, US state flags, genuine pirate flags of actual pirates, the Rainbow flag, US military flags and flags for international organizations like the United Nations.