JortK

This WordPress plugin will cleanup your WordPress database, which means that it will perform the following actions:
*Remove all post revisions
*Remove all spam comments
*Remove all unapproved comments
*Remove all unused tags
*Remove all unused post meta
*Optimize MySQL tables by removing all unused table space

WP-Cleanup

This Wordpress plugin will cleanup your Wordpress database by remove all unused data from your database.

Roger Rodrigo

Keep your WordPress fast and your database clean!
WordPress 3.6 allows users to control how many revisions are stored for each supported post type. 
This plugin provides an interface for this new functionality.
<h4>Why you should use this plugin?</h4>
Each time you click Save Draft or Update, a revision is saved on the database. 
WordPress will store all revisions for each page on your blog. Revisions allow you to look back at the recent changes you’ve made and revert to an earlier version if necessary.
But, what about all those revisions that you won’t use anymore? Yes, they are still there, taking space from your hosting space and increasing the volume of your database and making it slower and heavier!
With this plugin you can easily limit the number of revisions that you want to save, with this you are saving space on your database and keeping the overall site performance in good shape.
<h4>How can I change/limit the number of revisions stored on my database?</h4>
Once <code>WP Revisions Limit</code> plugin is installed and activated, go to Settings > Revisions Limit in your WordPress site and specify the number of revisions you want to store for each post/page under Revisions Options section.
<h4>Compatibility:</h4>
This plugin is fully compatible with any WordPress site with version 3.6 or higher.
Requires at least WordPress 3.6 and PHP 5.3
Please show your support for this plugin by giving it a <a href="https://wordpress.org/support/view/plugin-reviews/wp-revisions-limit?rate=5?rate=5#postform" rel="ugc">rating</a>
Development is on GitHub: https://github.com/rrodrigonuez/WP-Revisions-Limit
Pull requests are more than welcome!

WP Revisions Limit

Limit the number of revisions stored for your posts. Keep your WordPress fast and your database clean!

WP-Cleanup vs WP Revisions Limit