Git Kraken is a heavily advertised Git GUI. It is a free application for open source projects and $50/year for an individual license. Prior to finding Git Kraken, I used Atlassian SourceTree, which is also on this list and is free. I found that GitKraken has an easier to use interface for almost all basic Git tasks. Atlassian has a better code diff tool and is able to perform more complex operations, which Git Kraken has some difficulty with.