Best fast-loading social sharing buttons plugins for WordPress.
1Monarch Social Sharing

Monarch is a powerful and fast-loading social sharing plugin that supports 20+ social networks.
2MashShare

Other social buttons are often using external scripts which are increasing loading times.
MashShare is using NO external script dependencies. All code is loaded directly from your website and MashShare ensures yours and your visitors privacy!
3Sassy Social Share

Sassy Social Share is a lightweight free social sharing plugin that enables your website users to share the content over Facebook, Twitter, Google, LinkedIn, Whatsapp, Tumblr, Pinterest, Reddit and over 100 more social sharing and bookmarking services.
4Easy Social Share Buttons

Easy Social Share Buttons for WordPress is one of the best social sharing plugins on the market, as well as one of the most complete and optimized social share buttons packages. With a single plugin, the whole world of social media sharing is opened up to you: increase your shares, grow your profile, build your following, get new subscribers and drive more traffic.
5SocialFans

SocialFans is a responsive WordPress plugin displaying your social accounts fans, subscribers and followers number with a lot of features coming with 30 social networks like Facebook, LinkedIn, Pinterest, Twitter and 26 other social networks.
6ShareBang

ShareBang is a social share plugin for WordPress that will helps you to increase shares and traffic and grow your sales. ShareBang supports 42+ social networks including Whatsapp, Facebook Messenger, Telegram, Skype, Viber and more.
7Elfsight Social Buttons

Elfsight Social Buttons plugin allows your website’s visitors to share your content on any social media you choose. Promoting your online business in social networks is now a matter of the couple of clicks it takes to install the Social Share Buttons WordPress plugin. And the shortcode generator provided with the Share Buttons plugin makes it amazingly easy to install.
8Social Sharing (by Danny)

The simplest sharing links possible for Twitter, Facebook and Google+.
9Custom Share Buttons with Floating Sidebar

With this plugin, you can give users a tool to share your content, product details and other information on 9 social networking websites.
10WP Social Sharing

WP Social Sharing is a very lightweight and simple social sharing plugin. This plugin provide option whether you want to include plugin CSS/JS or not.
11Cresta Social Share Counter

Cresta Social Share Counter is a free WordPress Plugin that allows your users to share posts and pages easily using the social buttons of Facebook, Twitter, Google Plus, Linkedin and Pinterest.
12AddToAny Share Buttons

The AddToAny sharing plugin for WordPress includes Facebook, Twitter, Pinterest, Google, WhatsApp, LinkedIn, Tumblr, Reddit, and over 100 more sharing and social media sites & apps.
13Super Socializer

Integrate Social Login, Social Share and Social Comments at your website easiest and simplest possible way.
14MaxButtons

MaxButtons is a powerful WordPress button, share button and social icon plugin. It to creates great-looking CSS3 WordPress buttons on any post or page on your site.
15Ultimately Social

Pick from 16 stylish design styles for your social share buttons. Place the share buttons before or after posts, floating, via widget, via shortcode, or define the location on the page (top right, bottom left etc.