A Mass-renamer for files
Purrr will let you rename multiple files according to specified template. Templates are really a miniature programming language, with variables and stuff.
All that to let you automate not-so-fun task of doing zillions of almost identical renames by hand. If you have ever downloaded anime series where files had smart names like kimi_ga_ep1_divx_mp3[23ed4xc].avi through kimi_ga_ep13_divx_mp3[4c00ddd].avi, you'll surely get the idea.