Format Factory Old Version 3.0
You could queue up hundreds of files, and FF v3.0 would run them sequentially. Advanced users discovered you could also drop a folder full of .flv files (from early YouTube downloads) and convert everything to .avi overnight.
Version 3.0 had a built-in DVD ripper that could decrypt basic CSS-protected discs. While legally questionable, it was widely used to digitize personal DVD collections before streaming took over. format factory old version 3.0