If you use both git and Emacs but not magit, you're missing out. It's so good that it makes me keep Emacs open even when I'm using another editor or an IDE. These days pretty much everything has basic git integration, but few interfaces can match magit at doing non-trivial operations conveniently. With magit, it only takes a few keystrokes to selectively commit some changed lines, reword a past commit, do an interactive rebase, or use the reflog.