For both professional and personal use, I can list 2 that you likely haven’t heard of:
https://github.com/meowtec/Imagine Imagine PNG/JPEG optimization - it basically compresses images and photos so you can email lots of stuff back and forth without using the likes of WeTransfer.
https://ditto-cp.sourceforge.io/ Ditto Clipboard Manager - a multi clipboard for Windows. Ever try to paste something, only to realise you’ve already copied over it? Its use and helpfulness is so ubiquitous, I just could never live without it anymore.
Windows has a clipboard feature like that built in now. Press Win+V to enable it.
That’s a far cry from what Ditto can do.
FileOptimizer collects these sorts of apps and tries out each on your files to get the best compression. I use it every day, particularly for work.