Who is your best friend? If you want to know, this is an answer.
This plugin is not so practical, but might provide a bit interest:)
This plugin is still under development, therefore its specification will might be changed.
If you use Vundle it's very easy, you just run command :BundleInstall tacahiroy/vim-bestfriend
inside vim.
And also put Bundle 'tacahiroy/vim-bestfriend' into .vimrc.
If you use pathogen.vim, you just execute following:
cd ~/.vim/bundle
git clone https://github.com/tacahiroy/vim-bestfriend.git
If you use neither Vundle nor pathogen, copy autoload and plugin directory
into your $HOME/.vim directory.
* on Windows, you probably copy those files into _vim directory.
bestfriend.vim provides two commands to show your best friend, :Relationship and :RelationshipWith.
Actually bestfriend.vim provides several options.
Copyright (c) 2012 Takahiro Yoshihara. Distributed under the MIT License.