gitconfig - anything you do with the
git configcommand can also be placed in a .gitconfig runtime configuration file in your home directory. My main use case is aliases that save me a ton of typing. Simple shortcuts like "c = commit -m" are an obvious starting point. But git also has several commands with multiple, handy flags; for instance, my "sweet-looking but concise logs" alias is "l = log --pretty=oneline -n 20 --graph --abbrev-commit". I do not want to memorize and type that monster, not once, not ever. My entire .gitconfig can be found in my dotfiles repo.
gitsh - an interactive shell for git. If you're running a bunch of git commands in a row, enter
gitsh& run them without typing "git" over & over. This can be very useful as git commands tend to come in waves; "oh I need to commit these final changes, rebase, checkout master, & then merge this feature branch" is a common workflow, for example. Gitsh also displays repository information—the current branch & working directory status—in its prompt.
hub - a command-line tool for interacting with GitHub. I don't use this because it wouldn't gain me a whole lot of efficiency but I bet hub would be invaluable if you're an active GitHub user.
Git - this package is essential if you're working in Sublime Text. It gives access to all the common git commands—add, commit, diff, log—right in the command palette. You never have to leave your editor to access version control, you can stay in a single context & do everything you need. It's a huge boon to productivity. I use "Quick Commit" (adds and commits the file I'm currently viewing) all the time. I bet roughly a third of my commits are through that single convenience method.
GitGutter - highlights lines that have been changed, added, or deleted in the file you're viewing with coloring in the gutter. You can select from a few different styles of coloring. This is a small nicety most of the time but can be of great assistance when returning to a project that has a dirty working directory or stashed changes which you've forgotten.