TortoiseGit - TortoiseGit is an easy to use client for the Git distributed revision control system.
gitg - gitg is a git repository viewer targeting gtk+/GNOME.
GitKraken - The intuitive, fast, and beautiful cross-platform Git client.
Giggle - Giggle is a graphical frontend for the git content tracker (think of gitk on GTK+).
SourceTree - Mac and Windows client for Mercurial and Git.
git-cola - git-cola is a powerful GUI for git, a distributed revision control system.