Atla-Search plugin facilitates the searching of various Atlassian applications right from your JIRA instance! All you need is an Application Link between the host JIRA, where the plugin is installed, and other supported applications.
Add-ons by J-Tricks
Copy to Subtak plugin lets you copy the custom field values (not standard JIRA fields like summary or description) from parent issue to its subtasks on creation.
JQL Tricks plugin is a plugin which has a set of useful JQL Functions for JIRA. Those include simple JQL functions to complex ones.
Is project planning becoming a nightmare for you? Uses complex tools and still missing key details? Presenting the "Simplified Planner for JIRA" from J-Tricks. Create simple, yet effective, project plans