Paint.NET, Inkscape, Krita, CinePaint, ImageMagick (command line - yes, it can be very useful at times), and various others when certain needs dictate.

Also, Photoshop CS3 which is my last paid version (moreover, I can still reinstall it as Adobe temporarily released a general version with an unlocked key when it abolished the CS3 licensing server some years ago).

I even use IrfanView viewer as it has a nice batch converter (although it's no good for 48-bit work).

Frankly, there's no shortage of image editors even after eliminating GIMP and Photoshop.