CDP aka Composers Desktop Project is an offline sound transformation tool, started in 1986! It can do a wide variety of audio processing, from intense pitch shifting/time stretching to very unique effects which can lead to creative, unexpected results.
Examples of use
Create ambient atmospheres from anything, add a sci-fi touch to any sound, process files with superlong time-stretching, complex distorsions and filters, etc.
Pretty interesting results on vocals. Definitely a tool worth experimenting if you're into sound design!