There is probably no end to what you can achieve with WordPress if you are building a standard website/blog/portfolio. With tons of customization options available with the themes, there is nothing less you can achieve when it comes to functionality in WordPress using plugins.
Plugins play an important role in making a WordPress site easy to create/manage and reduces time and cost in development. However, selecting right plugin for a given functionality in WordPress is important. You may find many WordPress plugin to perform a task but the credibility of a plugin is a big question as it may contain poorly coded functions which either can bring your site down due to compatibility issues with other plugins or may create a glitch with a random update in future or open your backdoor leaving your security at risk.
Thus it is recommended to use plugins from the authentic and smart sources. How about Automattic? The makers of WordPress itself?
Most of WordPress users and novice developers knows about Jetpack, WP Super Cache. A few about Akismet and a fraction about VaultPress. But there are a few other plugins from Auotmattic which you may give a try…
Email Post Changes
Get notified upon a post/page change in WordPress. Check out this plugin if you want to know when an an update is made to an existing page/post.
Out of many popular WordPress security plugin, this one is comparatively less used by the WordPress community but this light weight plugin from BruteProtect (now aquired by Automattic) is an excellent choice for WordPress security.
Post Meta Inspector
This one is a good plugin for developers (mainly) which shows the post meta without digging into the database. If you are developing a theme or plugin which involves use of custom fields, you may need this one for developing smartly!
Get all the crap on the floor. With monster widget plugin, you can get all the available widgets right on one sidebar and you don’t have to drag each widget to a sidebar of your choice. Pretty cool for developers.
Run an awesome live feed on your WordPress website right from the front end without saving/updating a post. Create a post, and hit the live feed editor on the edit screen and get the ball rolling.
Easy Custom Fields
There is a popular one named Advanced Custom Fields but this one from Automattic is a cool one too.
WordPress.com Theme Updater
Get your WordPress.com plugins updated automatically without having to hit the
List of all plugins from Automattic, the makers of WordPress
Here is the complete list of plugins from Automattic. You can scroll around and see if there is something which you may add to your favorite WordPress plugins.