One that I find myself using probably more than I should is
undo
:
# undo the last commit
undo = reset --soft HEAD^
redo = reset 'HEAD@{1}'
Another is a quick update method for repos that I'm not contributing to, but might be dirty:
up = !git fetch && git rebase --autostash FETCH_HEAD
And for those times I forget those aliases I don't use as often:
# list aliases
la = "!git config -l | grep alias | cut -c 7-"