Flag waving is done by typing /f[country code] in the chat, where country code is the 2 letter country code. However as long as the first two letters are correct, the correct flag will be shown (ex: "france" / "frnc"). Typing in an incorrect country value will result in you waving a stick. Any values less than 2 characters are ignored.
Example: /f fr to wave the french flag.
List
You can find ISO codes by clicking one of the following external links: