Customize Anything
Add custom fields, tweak who sees what field and when, add your own issue types, priorities, status values. Setup Project and Version level attributes to store your key meta-data. Organize items into Schemes and apply them to multiple projects at once.
Customize each Project Dashboard to show key information.
Setup default values and hide fields to limit information required during issue creation or editing.
Even define when, where and who can see individual issue atrributes (e.g. only "Testers" can see/amend "Fixed In Version" issue attribute).
..and plenty more options to tweak Gemini to suit your business.