A simple useful application for Git's stash feature came about today when I started making some amendments to a repo master branch, forgetting I wasn't on my develop branch. I didn't want to make the changes to the master branch and I didn't want to have to copy the files between the two branches manually.
Git stash to the rescue:
$ git stash save
$ git checkout develop
$ git stash apply
$ git commit -m 'Apply stashed changes'