Best WordPress plugins (according to Kostas Krevatas)

Well here is the list:

Admin Columns

Customize columns on the administration screens for post(types), pages, media, comments, links and users with an easy to use drag-and-drop interface.

Advanced Custom Fields

Fully customise WordPress edit screens with powerful fields.

AK: Featured Post Sidebar Widget

Easily configure this widget to display any amount of posts (from 1 to 99) from a category into any widgetized area of your blog.

All in one Favicon

Easily add a Favicon to your site and the WordPress admin pages.

Clone Posts

Cloning posts and pages in WordPress.

Co-Authors Plus

Allows multiple authors to be assigned to a post. This plugin is an extended version of the Co-Authors plugin developed by Weston Ruter.

Contact Form 7

Just another contact form plugin. Simple but flexible.

Crayon Syntax Highlighter

Supports multiple languages, themes, highlighting from a URL, local file or post text.

Custom Post Type UI

Admin panel for creating custom post types and custom taxonomies in WordPress

Disable WordPress Core Updates

Disables WordPress core update checks and notifications.

Display Authors Widget

Register widget to display authors by role in a sidebar.

Duplicate Post

Clone posts and pages.

Dynamic Widgets

Dynamic Widgets gives you full control on which pages your widgets will appear.

Email Login

Allows you to log into WordPress (directly or via XML-RPC) using your email address instead of a(nother) username.

EP Social Widget

Very small and easy to use widget and shortcode to display social icons on your site. Facebook, Twitter, Flickr, Google Plus, Youtube, LinkedIn, DeviantArt, Meetup, MySpace, Soundcloud, Bandcamp, Pinterest, Vimeo and RSS feed

Events Manager

Event registration and booking management for WordPress. Recurring events, locations, google maps, rss, ical, booking registration and more!

FontAwesome Anywhere

This plugin allows users to add font awesome icon support to their website using HTML or built-in shortcode handler. It’s fully functional with Visual Composer Page Builder Plugin.

Google Analytics by Yoast

This plugin makes it simple to add Google Analytics to your WordPress site, adding lots of features, e.g. error page, search result and automatic outgoing links and download tracking.

Huge IT lightbox

Lightbox is the perfect tool for viewing photos.

iThemes Security

Protect your WordPress site by hiding vital areas of your site, protecting access to important files, preventing brute-force login attempts, detecting attack attempts and more.

Login Logo

Drop a PNG file named login-logo.png into your wp-content directory.

Login With Ajax

Ajax driven login widget. Customisable from within your template folder, and advanced settings from the admin area.

Maintenance

Take your website for maintenance away from public view.

Parent Category Toggler

Automatically toggle the parent categories when a sub category is selected.

Paste as Plain Text

Forces the WordPress editor to paste everything as plain text.

Regenerate Thumbnails

Allows you to regenerate all thumbnails after changing the thumbnail sizes.

Register Plus Redux

Enhances the user registration process with complete customization and additional administration options.

Rename wp-login.php (unmaintained)

Change wp-login.php to whatever you want.

Reveal IDs

Reveals hidden IDs in Admin interface that have been removed

Rewrite Flush Button

Adds a ‘Flush Rewrite Rules’ button to WP-Admin > Settings > Permalinks.

ScrollTo Top

Uses the jQuery plugin ScrollTo by Ariel Flesler to smoothly scroll the user’s browser to the top of the page when the user clicks the unobtrusive go-to-top image.

Shortcode Widget

Adds a text-like widget that allows you to write shortcode in it. (Just whats missing in the default text widget)

SMK Sidebar Generator

This plugin generates as many sidebars as you need. Then allows you to place them on any page you wish.

Sticky Custom Post Types

Enables support for sticky custom post types. Set options in Settings → Reading.

SuperSlider-Perpost-Code

Write css and javascript code directly on your post edit screen on a per post basis. Meta boxes provide a quick and easy way to enter custom code to each post. It then loads the code into your frontend theme header and or footer if the post has custom code.

Ultimate Posts Widget

The ultimate widget for displaying posts, custom post types or sticky posts with an array of options.

Ultimate TinyMCE

Beef up your visual tinymce editor with a plethora of advanced options.

User Role Editor

Change/add/delete WordPress user roles and capabilities.

User Switching

This plugin allows you to quickly swap between user accounts in WordPress at the click of a button.

WordPress Database Administrator

WordPress Database Administrator plugin for WordPress Database Access. Simple but Powerfull.

WordPress Language

Easily switch languages and download translations for WordPress

WordPress SEO

The first true all-in-one SEO solution for WordPress, including on-page content analysis, XML sitemaps and much more.

WP Admin No Show

Efectively blocks admin portion of site for selected user roles.

WP Custom Admin Bar

Easily add your own link or logo to the WordPress Admin Bar. Then highlight important links for your users through a simple drop-down menu!

WP e-Commerce

A plugin that provides a WordPress Shopping Cart.

WP e-Commerce Style Email

Style the emails that WP E-Commerce sends to your customers.

WP htaccess Control

Interface to customize the permalinks (author, category, archives and pagination) and htaccess file generated by WordPress.

WP Super Cache

Very fast caching plugin for WordPress.