Sovit Tamrakar

World Flag is WordPress Flag Plugin which will ease the writer/authors to add flags to posts or pages with shortcode.
Tinymce Editor button has been added to ease the usage of plugin with few clicks of button.

World Flag

World Flag - Country Flag using shortcode.

Adnan Haque (a11n)

Time for moderators and blog monitors to take rest. Let the visitor choose what they want to see in the blog. Visitor can flag unsuitable posts. After a number of flags the post status will be changed to anything you want. You can change the post status to Draft, Pending Moderation, Moderated(custom status) or send the post to trash, remove it permanently. You can also set it to do nothing if you plan something else. You can have a notification if the post is flagged number of times you will have set.
You can exclude some categories and mark some users as safe to remove the flag option from there posts.
You can track visitors by IP, Cookies and user id to prevent multiple flags. You can chose who can flag by user roles.
The plugin is css frienfly. You will be able to customize the posts by the number of time they have flagged.
More details on the documentation page after installing the plugin.

Virtual Moderator

This plugin helps to keep community blogs clean. There must be some unwanted posts if blog is open for anyone. It Lets visitors to flag those posts.

World Flag vs Virtual Moderator