Finds identical pictures, documents and any other files
Compares files not only by names, but by their content
Can significantly increase free space on your disk
Helps you to organize your media collections
Reduces time needed to defragment your hard drive
I use this to check my work before handing in the assignment which is then scanned by Turnitin by the university. I always pass the Viper test and the Turnitin test (no surprise there since I never copy for my uni work).