Lorna Timbah

This plugin creates a widget to show the top commentators in your WP site. Always go back to the Widget settings after each version update to Save your settings. Demo can be found at http://demo.webgrrrl.net
The Top Commentators Widget plugin is adapted from Show Top Commentators plugin at Personal Financial Advice, this widget is easier to manage via the control form (no need to edit the PHP file); additional options are also available to make it more flexible. Read the FAQ section on how to customize the widget. Read the Changelog as well as http://webgrrrl.net/tags/tcw for the latest news on this widget.
This widget is extensively tested with the following settings: Google Chrome 13.0.782.215 m, PHP 5.2.13, Apache 2.2.15 (Win32), MySQL 5.0.51a, WordPress 3.2.1. Further testing and bug report on this widget is greatly welcomed and appreciated.

Top Commentators Widget

Adds a sidebar widget to show the top commentators in your WP site. Demo: http://demo.webgrrrl.net

FolioVision

There’s one problem with Gravatars. They are very slow to load. Each page with comments on them makes one call per comment to the Gravatar server. While a single call takes only a 100ms, on a page with hundreds of comments, we are talking about major slowdowns. Page loads can take 20 seconds and more.
This plugin solves this problem by:
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caching gravatars with WordPress cron job..
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<li>
caching gravatars on comment submission
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<li>
maintaining a single copy of the default gravatar instead of downloading it again and again for all the email addresses with no gravatar associtated
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</ul>
<a href="http://foliovision.com/seo-tools/wordpress/plugins/fv-gravatar-cache/installation" rel="nofollow ugc">Installation guide</a>
<a href="http://foliovision.com/seo-tools/wordpress/plugins/fv-gravatar-cache" rel="nofollow ugc">Support and more information</a>

FV Gravatar Cache

I deactivated plugin but still contains elements in Database

Database Junk

Speeds up your website by making sure the gravatars are stored on your website and not loading from the gravatar server.

Top Commentators Widget vs FV Gravatar Cache