This plugin brings the power of @mention inside tinyMCE. You can choose where the autocompletion gets his information from and on which custom post type this plugin is activated on. You can also create custom template replacement on the front-end based on your needs.
A review of the plugin is available on WP Tavern.
Development of this plugin is done on GitHub. Pull requests welcome. Please see issues reported there before going to the plugin forum.
This plugin is available for download for your site.