In my experience, this is the best, because it is very easy to organise your working process. I like the system of filters and boards it has. I have tried other stuff too, like Asana, Jira, even Monday. Those have their pros and cons too, but to me personally Youtrack is the preferred one, due to it's simplicity and inherent minimalism. I don't do rocket science, so maybe that's why I find it the most compelling.
GitHub - Originally founded as a project to simplify sharing code, GitHub has grown into an application used by over a million people to store over two million code repositories, making GitHub the largest code host in the world.
Jira - The #1 software development tool used by agile teams. Jira Software is built for every member of your software team to plan, track, and release great software.
Phabricator - Phacility - Phabricator
OneLogin - On-demand SSO, directory integration, user provisioning and more
BitBucket - Bitbucket is a free code hosting site for Mercurial and Git. Manage your development with a hosted wiki, issue tracker and source code.
AuthAnvil - AuthAnvil software is an integrated identity and access management tool designed to help IT managers service their networks, infrastructure network, and ensure that devices are safe and secure at all times. Read more about AuthAnvil.