Sana Azmeh

Save your important posts, so you can return to them at any time and read or view them again.
<ul>
<li>
To add post to your list press Fave it button, then add tags and press enter
</li>
<li>
To remove post from your list press Unfave it button
</li>
<li>
You can style the button as you want or it gets the default style matching the template
</li>
<li>
To add post to faves list use shortcode [myfaves-add]
</li>
<li>
You can add the shortcode in sidebar or footer widget or below header.
</li>
<li>
To list the faves use shortcode [myfaves-list]
</li>
<li>
To list faves tags or collections use shortcode [myfaves-tags]
</li>
<li>
Fave tags links will list posts related to specific tag for logged in user
</li>
</ul>

My Faves for WP

Save your favorite posts, add tags, and list them.

Huseyin Berberoglu

Allows users to add favorite posts. This plugin use cookies and database for 
saving data.
<ul>
<li>If a user logged in then favorites data will saved in database instead of cookies.</li>
<li>If user not logged in data will saved in cookies.</li>
</ul>
You can choose “only registered users can favorite a post” option, if you want. 
Also there is a widget named “Most Favorited Posts”. And you can use this template 
tag for listing most favorited posts;
Most Favorited Posts
If you use WP Super Cache you must add page (which you show favorites) URI to “Accepted Filenames & 
Rejected URIs”.
If you need support <a href="https://wordpress.org/support/plugin/wp-favorite-posts" rel="ugc">create a topic on support forum</a>
Please submit your pull requests to https://github.com/hberberoglu/wp-favorite-posts

WP Favorite Posts

Allows visitors to add favorite posts. This plugin use cookies for saving data so
unregistered users can favorite a post.

My Faves for WP vs WP Favorite Posts