AutoHotkey Is an amazing scripting language.
Gimp If you want to edit images, you can not get much better.
Libre Office For editing Microsoft Office files.
LMMS Write music using this FL Studio inspired program.
Blender is an amazing 3D modelling program.
Audacity is a great audio editing program.
Anti-Twin searches directories for duplicate files. Works great for images but will work with any file type.
AOMEI Backupper is an amazing program for creating backups of your system. It allows you to do incremental backups as well.
Macrium Reflect is another great program for creating backups.
Alternative to is a great site to find programs that work similar to others but usually for free.