I was looking for a portable Git GUI Client and I finally have found what I wanted, it is SmartGit.
SmartGit is a smart, intuitive and easy Git client much suited for beginners like me. It has a rich interface full of features, is light on disk and works right out-of-the box.
I was surprised to see that it supersedes Github native client when the ease of usage is compared and so becomes the best tools for git beginners in my view.
A portable version of SmartGit can be downloaded from Syntevo's site. The portable version ships with the needed Java Runtime Environment files (JRE) and doesn't interfere with the installed Java version. SmartGit requires Git to be installed and luckily Windows version of Git ( mysisgit) comes with a portable version. The portable version can be downloaded from Google code downloads repository.
Note - Google Code is deprecating downloads so you may probably will not see mysisgit downloads there if you are reading this after Mar 2014.
25/1/2014, the latest version of portable mysisgit can be downloaded from this link.
Once you have downloaded and unzipped portable git (mysisgit), you can put it in the SmartGit folder as below.
Then run SmartGitHg.exe from the bin folder, follow the instructions and you are all set up for managing your git projects.
CAUTION - The folder structures as used in this post may differ from the original portable version as I am using a custom launcher.