baxeico

This plugin allows to mention WordPress users in a comment by writing usernames preceded by a character (default @), e.g. @guguweb. 
The mentioned users will receive a notification email with a link to the relevant post.
The mention character (default @) can be customized by a filter hook: <code>cum-mention-char</code>. Put the following code in your theme <code>functions.php</code> file:
<pre><code>add_filter( 'cum-mention-char', 'cum_custom_char' );
function cum_custom_char( $content ) {
 return '+';
}
</code></pre>
And the mention character will be +, so you can mention with +guguweb.
This plugin was inspired by <a href="https://wordpress.org/plugins/mention-comments-authors/" rel="ugc">Mention comment’s Authors by Wabeo</a>. Many thanks to the <a href="http://wabeo.fr" rel="nofollow ugc">author</a>!

Comments Users Mentions

Allows to mention Wordpress users in a comment. The mentioned users will receive a notification email.

wladweb

Plugun show twitter user timeline, home timeline, mentions, home timeline another user, search result by post tags, category name and any words. 
Tweets can be show in widget and also in home page between posts in main loop.

Tweettee

Plugin can show tweets in widget and in home page.

Comments Users Mentions vs Tweettee