Some Wordpress plugins are often updated, which is good think. Plugins that are updated are 100% compatible with last Wordpress version and they also are the most secure possible. A plugin that has not been updated for a long time might not work with last Wordpress version and might create a security breach for you website.
Extended Comment Options allows you to close or open comments on batches of posts. You can schedule this automatically, too.
Customizable jQuery accordion for Wordpress which gathers Facebook social plugins together .
Allows you to add a lightweight jQuery based featured content slider anywhere on your theme.
The "Smart DoFollow" plugins lets you automatically give DoFollow links to authors of comments that are longer than a given number of chars.
This plugin makes it easy to administer and display matches (sports or otherwise) with a neat widget.
Posts your blog posts to one or multiple Status.net servers and even to Twitter
Lets you insert a Google+ Page Badge to your site via shortcode. Easy to intall and implement.
Wordpress tiniest cache plugin ever with just 2KB engine. Boost your page load time 10000 times faster, and save lots of your memory.