Plugins: TweetMeme Retweet Button

What it is: Easily allows your blog post or page to be retweeted. It provides a live count of how many times your post/page has been retweeted throughout Twitter.

Features

• Support for the Twitter Tweet button
• Live count of tweets from Twitter
• Allows you to change the source which you retweet, E.g. ” via @”
• Easily installation and customisation
• Quicker loading times for the buttons
• Hashtag support (which are automatically taken from your post tags)

More info: https://wordpress.org/plugins/tweetmeme/