Etcher is an easy-to-use cross-platform tool for burning images to SD cards, USB drives and other removable devices.
The program keeps operations to the bare minimum, all of them clearly displayed on a simple interface. Choose your image, then your drive, and finally click the "Flash!" button.
Etcher supports many different image formats: ISO, IMG, RAW, BZ2, DMG, DSK, ETCH, GZ, HDDIMG, XZ and ZIP.
The "Choose a drive" step only allows selecting removable devices, reducing the chance that you'll accidentally trash a fixed drive. If this doesn't suit your needs - maybe a removable device isn't being detected correctly - you can disable this protection by turning on "Unsafe Mode" in settings.
Once the image is written, Etcher validates the results to make sure it's worked correctly. That's usually a good idea, but can take a while, and if you prefer you can disable validation in Settings.