alt Hacker News> Magit is absolutely the best Git GUI ever.
But it isn't graphical :-P.
Personally i've been often looking for an opensource Git GUI front end but couldn't find anything i'd like. My points of reference of decent tools -ignoring the underlying tech- are Perforce and TortoiseSVN under Windows and Fuel[0] (for Fossil) and KDESVN under Linux.
Perforce and Fuel are the two i like the most, followed by KDESVN and Tortoise. But since i'm on Linux and i stick with opensource projects, Perforce and Tortoise are out, leaving me with Fuel and KDESVN. I'm using KDESVN for a few projects where i don't care about external collaboration and want to store many binary files (which Subversion does it better that Git IMO), though KDESVN is very primitive and limited in what it supports (it doesn't support shelving at all, for example - in fact for anything beyond commit and checking the history you probably need to use the cli tool). I do not use Fossil much nowadays but i used it a lot in the past so i have a bunch of repositories in it, for which i use Fuel. Fuel is unfortunately not being developed anymore, though since it is opensource it doesn't matter much (which is a reason why i ignore anything non-opensource, i know there are some decent proprietary Git clients but for me they might as well not exist).
I think at some point i'll grab libgit2 and make something using Lazarus, probably something similar to Fuel. Unlike libsvn, which seems to be made in hell, libgit2 seems very sane and shouldn't be terribly hard to make something usable out of it.
In the meanwhile i use a combination of git cola, gitgui and gitk though they all feel like a hodgepodge of barely thought random features thrown in together (and i hate that they all want to impose their own idea of how i should format a message -especially git cola- which of course aren't identical between of them and aren't even close how i'd like to format the messages myself).