When writing large documents with a text editor, it is sometimes useful to zoom out and get a high-level view of the file (I believe Sublime Text has a feature called minimap that does this). This functionality can be added to gVim with a simple vimrc addition (to my knowledge, this will not work with regular Vim).
Add the zoom out command with the following:
noremap <Leader>zo :set guifont=courier_new:h4<CR>
Add the zoom in command with the following:
noremap <Leader>zi :set guifont=courier_new:h10<CR>
Adjust the font type and normal size as desired. Not the most elegant method but it works. Please note that split window sizes may be affected during the zooming process (it is a hack after all).