Jira may be extremely sluggish and require a large amount of memory on the client side.
Trello - Infinitely flexible. Incredibly easy to use. Great mobile apps. It's free. Trello keeps track of everything, from the big picture to the minute details.
Linear - Streamlined issue tracking for software teams
Asana - Asana project management is an effort to re-imagine how we work together, through modern productivity software. Fast and versatile, Asana helps individuals and groups get more done.
Distiller - Distiller's hosted continuous integration platform takes the pain out of mobile development through automated build, test, and deployment of your iOS apps.
Wrike - Wrike is a flexible, scalable, and easy-to-use collaborative work management software that helps high-performance teams organize and accomplish their work. Try it now.
BugHerd - BugHerd: The Website Feedback Tool for Agencies