For client projects I'm a big fan of Lighthouse (https://lighthouseapp.com/). It has a great balance of advanced features and ease of use for non-techies.
* Tickets can be created and updated via email
* Using the GitHub service hook, you can tag commit messages so that they appear as comments on a ticket as well as change the state of the ticket (For example: "Refactor widget behaviour [#123 state:resolved]")
* You can setup milestones (with or without a due date) and assign tickets to them
* Bulk editing of tickets
* Markdown in ticket description and comment fields
* You can easily create "buckets" of tickets based on search terms and filters
* Bugsnag and Airbrake can be configured to automatically create tickets for new exceptions in your app
* Probably some other great features that I've forgotten to mention
* Tickets can be created and updated via email
* Using the GitHub service hook, you can tag commit messages so that they appear as comments on a ticket as well as change the state of the ticket (For example: "Refactor widget behaviour [#123 state:resolved]")
* You can setup milestones (with or without a due date) and assign tickets to them
* Bulk editing of tickets
* Markdown in ticket description and comment fields
* You can easily create "buckets" of tickets based on search terms and filters
* Bugsnag and Airbrake can be configured to automatically create tickets for new exceptions in your app
* Probably some other great features that I've forgotten to mention