WizTree

vs

DiskImager

TreeSize is a disk space manager for Windows. The application is used by over 100,000 people to identify where storage space is going. TreeSize provides a visual representation of your harddrive, and tools to clean up unwanted files to increase overall storage space.

GNOME Disks is a free and open-source GUI for the gnome-disk-utility package. GNOME Disks can be used for partition management, monitoring, benchmarking, and software RAID.

DaisyDisk is a freemium disk analyzer application for macOS. With DaisyDisk you can visualizes hard disk usage and get a broad overview on how to free up hard disk space. Through an intuitive interface with an interactive sunburst chart that you can use to easily navigate your hard disk, and free up space by deleting large files that you don't use.

A really simple open-source, GUI application that writes compressed disk images to USB drives and creates backups. USBImager is avalible for Linux, macOS, and Windows.
 

UNetbootin, short for Universal Netboot Installe is a tool that allows you to easily create bootable USB flash drives to install or try operating systems. This software is designed to be cross-platform and works with Windows, as well as Mac and Linux operating systems.

With Rufus you can format and create bootable USB drives. Rufus is free and open source and can format FAT, FAT32, NTFS, exFAT, UDF, ReFS that works across USB flash drives, keys, and memmory sticks.