Favorites is a very flexible add-on that enables your members to save and remove channel entries as favorites/bookmarks. Members can view the entries they've saved to their favorites, and/or view others favorites. Additionally, your members have the choice of saving entries as public or private favorites.
The Favorites:Rank tag shows which entries have been favorited the most, and how many times. Favorites:Author_Rank shows the top ranked authors of entries saved to other member's favorites, as well as the total amount of times their entries have been saved to favorites.
Favorites also lets you to show all members who saved a particular entry, as well as other entries those members also saved to their favorites.