My personal .gitconfig (mostly stolen from others) :-)

.gitconfig

[user]
    # Credentials.
    name = Foo Bar
    email = foo@bar.com
    drupal = $(whoami)

[credential]
    # Save passwords in ~/.git-credentials.
    helper = store

[core]
    bare = false
    filemode = true
    ignorecase = true
    logallrefupdates = true
    quotepath = false

    # Fix whitespace errors.
    whitespace = fix,-indent-with-non-tab,-indent-with-tab,trailing-space,cr-at-eol

    # Global .gitignore file.
    excludesfile = ~/.gitignore

    # Use "less" as the pager. This will provide nice colors.
    pager = less -R

[apply]
    whitespace = fix

[branch]
    # automatically link new branch to start-point branch (upstream)
    autosetupmerge = true
    autosetuprebase = always

[help]
    # wait .5 seconds before autocorrecting
    autocorrect = 5

[push]
    # Ensure that when you `git push` only the current branch is pushed rather than all branches (why is this not the default)
    default = current

[rerere]
    # Reuse recorded resolution of conflicted merges:
    # - http://shop.oreilly.com/product/0636920024774.do
    # - http://git-scm.com/2010/03/08/rerere.html
    enabled = true

[color]
    ui = auto

[color "branch"]
    current = yellow reverse
    local = yellow
    remote = green

[color "diff"]
    meta = blue bold
    frag = magenta bold
    old = red bold
    new = green bold
    whitespace = red reverse

[color "status"]
    added = yellow
    changed = green
    untracked = cyan

[alias]
    # list aliases
    aliases = !git config --list | grep 'alias\\.' | sed 's/alias\\.\\([^=]*\\)=\\(.*\\)/\\1\\\t => \\2/' | sort

    # shortcut for 'git status'
    st = status

    # shortcut for 'git commit'
    ci = commit

    # shortcut for 'git branch'
    br = branch

    # shortcut for 'git checkout'
    co = checkout

    # shortcut for 'git diff'
    df = diff

    # shows an abbreviated git log with nice formatting
    lg = log --graph --pretty=format:'%Cred%h%Creset -%C(yellow)%d%Creset %s %Cgreen(%cr)%Creset' --abbrev-commit --date=relative

    # performs 'git stash', 'git pull' and 'git stash pop' in a sequence
    pu = !git stash && git pull && git stash pop

    # removes all unstaged files except for .patch files.
    cn = clean -df --exclude=*.patch

    # locate commit where a particular file was introduced
    added-file = log --diff-filter=A --

    # list contributor stats for this repo
    contributors = !git shortlog -n -s --no-merges $@ | cat - && echo && echo total $(git rev-list --count HEAD)

    # list commits not yet pushed to remote
    local = log --branches --not --remotes

    # show branches that have been merged into current (HEAD) branch
    merged = !git fetch --all && git branch --all --merged HEAD

    # show branches that have not been merged into current (HEAD) branch
    not-merged = !git fetch --all && git branch --all --no-merged HEAD

    # decorated graph view of one liner summarized commits from all branches. (inspired by git-extras)
    tree = log --all --graph --decorate --oneline --simplify-by-decoration

    # stage and commit given file
    checkin = !git stage "$*" && git commit $!

    # undo local changes
    undo = checkout --

    # remove staged changes from the index: (1) provide file name/pattern (2) otherwise, removes all
    unstage = reset HEAD --

    # count modified files
    count-modified = !echo $(git status --porcelain | grep -E '[^MARC]' | wc -l | awk '{ print $1 }') files modified

    # clone a d.o project.
    dc = !sh -c 'git clone $(git config --global user.drupal)@git.drupal.org:project/$1.git $@' -

    # creates a d.o change notice.
    change-notice = "!f() { echo '<ul>' && git log $1..$2 --reverse --pretty=format:'<li><a href="http://drupalcode.org/project/'$(basename `git rev-parse --show-toplevel`)'.git/commit/%H">(view commit)</a> %s</li>' && echo '</ul>'; }; f"

Very nice!
I also do:

[diff]
  algorithm = patience

[merge]
  ff = false

The 'contributors' alias is listed twice

Whoops, thanks... Fixed.