Asana Importer Plugin for JIRA helps to migrate smoothly all of the existing tasks to Jira. It allows you to ma
nage the workflows and customize the board. Great for making first steps with Jira, as you can immediately evaluate the tool with real data.
JIRA Software (previously JIRA Agile / GreenHopper) add-on that provides Agile
Scrum methodology for your JIRA tasks. Half of all the Atlassian users have this add-on installed. It is constantly updated, can be easily customized, which is always a big plus.
ScriptRunner for JIRA, if you prefer Groovy scripting. This add-on provides a platform to 
transform your JIRA into a more powerful workhorse than it already is. It has built-in administration support, a set of JQL and workflow functions.
JIRA Suite Utilities and JIRA Toolkit add-ons provide extensions to workflows and new custom fields. New validators and post- functions can also be useful. The add-on provides a transition summary tab and custom fields for Google maps locations.
Tempo Timesheets, in case if you are a fan of timesheets. Almost 7000 customers around the world are already using this add-on so it might give you a hint to try it out. With this plugin, you have effortless time-tracking, flexible reporting, and operations management.
Hip-Chat for Confluence lets you share information and collaborate. It sends notifications of almost any kind and helps you stay in touch with your team at any time in any place.
Balsamique is our personal preference. It is a rapid wireframing tool that reproduces the 
experience of sketching on a whiteboard. You can produce the mockups fast to find the best solutions for your projects.
Team Calendars for Confluence is perfect for team or event calendars. It is called a single 
source of truth – as it manages team leave, tracks Jira projects and plans events. It seamlessly connects Jira and Confluence.
Confluence Roadmap Plugin to create a visual roadmap of the milestones, features, and themes. With this add-on it is easy to make sure that everyone is one the same page.
Gliffy Diagrams for Confluence is the most popular diagram creating tool for Confluence in Atlassian ecosystem