Gunar

Allow site visitors to share your blog posts or pages via favorite social networks, attracting more visitors to your site. Facebook, Twitter, Google+ and many more included.
Several different styling and hover effects implemented for easier in-site outlook integration.
Insert anywhere in the post via shortcode, or, include in every post/page (at beginning and/or bottom) automatically (convenient way for large wordpress installations with many entries, with ability to exclude from particular post/pages).
Adventages
<ul>
<li>Lightweight – short code, plugin is doing exactly what is meant for </li>
<li>Fast – no extensive use of processing time</li>
<li>Device friendly – it will look handsome on PC, mobile or tablet</li>
<li>Browser friendly – Chrome, Firefox, Safari and IE tested</li>
<li>Theme friendly – tested on various WordPress themes (but we strongly recommend you to test the plugin in your own theme)</li>
</ul>

Goo Share This

Allow site visitors to share your blog posts or pages via favorite social networks, attracting more visitors to your site.

Sibin Grasic

Select to Share WordPress plugin will allow you to easily display a nice pop-up menu on text selection. 
CSS selector option is provided so you can target only your post / page content.
Features
<ul>
<li>Automatically displays a nice pop-up menu on text selection (highlight)</li>
<li>Mobile fallback with pop-under sharing menu</li>
<li>Highly compatible – you can change the css selector for the text highlight</li>
</ul>

Select to Share

Nice

Show a nice pop-up menu on text selection for sharing on Facebook, Twitter and e-mail...

Goo Share This vs Select to Share