Google analytics counter tracker - analyse the visitors hits on you website and display it graphically
Use Firebug with FirePHP to analyze the SQL queries made by WordPress. Ideal for development and avoid performance issues.
The Plugin Debug Objects provides a large number of information: query, cache, cron, constants, hooks, functions and many more.
Adminer is a full-featured MySQL management tool written in PHP. This plugin include this tool in WordPress.
List query-actions only for admins; for debug purposes
Facebook Like Lock for WordPress. Locks your content and user can unlock by clicking on like button.
Like Gate allows you to reveal some hidden/secret content when the user likes the article. Therefore increasing the likeness of your articles.
Work with FirePHP, only PHP5 and a sample af values of WordPress
This plugin adds a Like-Button wherever you want on your blog. Before or after the content as well as a sidebar-widget. And many more!
Stalker Tracker is a tool designed for unpopular bloggers to track stalkers on their blogs, typically their ex-boyfriends/girlfriends.