Issue Checklist add-on allows users to add simple ToDo list to an issue and watch the progress when succeeding items from the list are completed.
Recurring Tasks plugin allows to schedule and create issues automatically on specified date and time. It supports well known cron format as well as graphical UI scheduler.
Automated Log Work
JIRA Cloud, JIRA Server
Automated Log Work allows to track time seamlessly in JIRA and JIRA Agile. It offers manual and automated mode so users can pick up the one that suits them best.
Default Values for Create Issue
Default Values plugin allows to automatically inject predefined values into fields on the "Create Issue" screen. It supports both system and custom fields.
Hide Time Tracking
JIRA Server, Data Center, JIRA Cloud
Hide Time Tracking plugin allows to hide time tracking information in JIRA UI from users who are not allowed to log work (users without "Work on Issues" permission).
Text Highlighter plugin allows to easily highlight selected text on a Confluence page or a blog post.
It offers similar features to iBooks and Kindle apps highlight capabilities.