Questions about tools for: the favorite question feature, the favorite tags feature, or extending "favoritism" to other features.
Here on Stack Apps, use this tag for the general act of favoriting (questions, tags, answers, comments, etc.).
From Meta Stack Exchange (tag wikis):
Favorite questions are marked by clicking the star below the question's score. It is searchable by using the
mineto search your personal set of favorites).
"Favorite tags" are a set of tags that can be marked by a user. The questions that have favorite tags will be highlighted, and can be monitored using Tag Sets.
There is no built-in capability to favorite answers or comments, but people have created tools to simulate such.