SourceTree - Mac and Windows client for Mercurial and Git.
GitKraken - The intuitive, fast, and beautiful cross-platform Git client.
GitLab - Create, review and deploy code together with GitLab open source git repo management software | GitLab
SmartGit - SmartGit is a front-end for the distributed version control system Git and runs on Windows, Mac OS...
BitBucket - Bitbucket is a free code hosting site for Mercurial and Git. Manage your development with a hosted wiki, issue tracker and source code.
GitHub Desktop - GitHub Desktop is a seamless way to contribute to projects on GitHub and GitHub Enterprise.