Advanced Excerpt
http://wordpress.org/extend/plugins/advanced-excerpt/
Several improvements over WP's default excerpt. The size can be limited using character or word count, and HTML markup is not removed.
AddQuicktag
http://wordpress.org/extend/plugins/addquicktag/
This plugin make it easy, Quicktags add to the html - and visual-editor.
Clean Notifications
http://www.mikeindustries.com/blog/clean-notifications
In a nutshell, it reformats the emails WordPress sends you when you get a new comment or ping so that they look nicer and take up less space.
Live Comment Preview
http://wordpress.org/extend/plugins/live-comment-preview/
Displays a preview of the user's comment as they type it.
WP-Markdown
http://wordpress.org/extend/plugins/wp-markdown/
Allows Markdown to be enabled in posts, comments and bbPress forums.
Jetpack by WordPress.com
http://wordpress.org/extend/plugins/jetpack/
Supercharge your WordPress site with powerful features previously only available to WordPress.com users.
VaultPress
http://vaultpress.com/
The world’s best WordPress security, backup, and support.
W3 Total Cache
http://wordpress.org/extend/plugins/w3-total-cache/
Improve site performance and user experience via caching: browser, page, object, database, minify and content delivery network support.
WordPress SEO Plugin
http://yoast.com/wordpress/seo/
WordPress SEO is the most complete WordPress SEO plugin that exists today for WordPress.org users. It incorporates everything from a snippet preview and page analysis functionality that helps you optimize your pages content, images titles, meta descriptions and more to XML sitemaps, and loads of optimization options in between.
WP Mail SMTP
http://wordpress.org/extend/plugins/wp-mail-smtp/
Reconfigures the wp_mail() function to use SMTP instead of mail() and creates an options page to manage the settings.
Artiss YouTube Embed
http://wordpress.org/extend/plugins/youtube-embed/
A simple to use method of embedding YouTube videos into your posts and pages but with powerful features for those that need them.
Google Analyticator
http://wordpress.org/extend/plugins/google-analyticator/
Adds the necessary JavaScript code to enable Google Analytics. Includes widgets for Analytics data display.
Ultimate Maintenance Mode
http://wordpress.org/extend/plugins/ultimate-maintenance-mode/
Work on your website behinds the scenes while you display a Maintenance Mode page to your visitors.
Contact Form 7
http://wordpress.org/extend/plugins/contact-form-7/
Just another contact form plugin. Simple but flexible.
WP-Memory-Usage
http://wordpress.org/extend/plugins/wp-memory-usage/
Show up the PHP version, memory limit and current memory usage in the dashboard and admin footer
Advanced Custom Fields
http://wordpress.org/extend/plugins/advanced-custom-fields/
Fully customise WordPress edit screens with powerful fields. Boasting a professional interface and a powerfull API, it’s a must have for any web dev
Custom Post Type UI
http://wordpress.org/extend/plugins/custom-post-type-ui/
Admin UI for creating custom post types and custom taxonomies in WordPress
WordPress to Buffer
http://wordpress.org/extend/plugins/post-to-buffer/
Publish your posts to Twitter, Facebook and LinkedIn via your Buffer account.
WP Smush.it
http://wordpress.org/extend/plugins/wp-smushit/
Reduce image file sizes and improve performance using the Smush.it API within WordPress.
WP-DBManager
http://wordpress.org/extend/plugins/wp-dbmanager/
Manages your WordPress database.
Revision Control
http://wordpress.org/extend/plugins/revision-control/
Revision Control allows finer control over the Post Revision system included with WordPress
Better WP Security
http://wordpress.org/extend/plugins/better-wp-security/
The easiest, most effective way to secure WordPress. Improve the security of any WordPress site in seconds.
Visual Composer for WordPress (from Themeforest)
http://codecanyon.net/item/visual-composer-for-wordpress/242431
Visual Composer for WordPress will save you tons of time working on the site content. Now you’ll be able to create complex layouts within minutes! It’s build on top of the modern technologies – get the best for your lovely website!