The Flags plugin allows small flags to be displayed in posts or pages using a shortcode.
For example, to display the flag of the United Kingdom of Great Britain & Northern Ireland, you would use this shortcode [flag=gb] and it would show 
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The plugin contains 252 flags; more flags in PNG format can be added simply by dropping them into the plugin’s images folder and using the filename in the shortcode.
Complimentary Plugins
azurecurve has the following plugins which allow shortcodes to be used in comments and widgets: