Gitscout - A beautiful Github Issues experience for macOS
Traq - Traq is a PHP powered project manager and issue tracker featuring multiple projects, milestones...
Zokyo - GitHub Chrome Extension to track and manage issues
16bugs - 16bugs is an all-in-one bug tracking software that makes it easier for you to manage all sorts of bugs in performance with the simple interface; ultimately, you will be more productive for sure.
GitHub Reader - A quick way to browse GitHub issues and pull requests.
Bugify - Bugify is a simple PHP issue tracker, designed to offer powerful bug tracking capabilities in an easy to use system.