Claude Vedovini

A plugin that uses the featured image in your posts as a favicon for 
that post. You can also set a default favicon and use it as a default featured 
image.
<h3>Privacy Policy</h3>
This plugin does not collect any personal information from your visitors.

Featured Favicons

A plugin that uses the featured image in your posts as a favicon for

Chip Bennett

As of WordPress 4.3, this Plugin is no longer needed. The next update will integrate the Plugin into the core site icon feature, to allow for graceful 
retirement of the Plugin.
Add a Favicon to your site. No bells or whistles; simply upload a (ICO, PNG, or GIF) file.
Note: Plugin settings can be configured via Dashboard -> Settings -> Favicon.

cbnet Favicon

Add a Favicon to your site. No bells or whistles; simply upload a (ICO, PNG, or GIF) file.

Featured Favicons vs cbnet Favicon