Been awhile since I saw a thread like this and they’re always good for at least one or two things I’ve never heard of before. Bonus points if the software is open source and cross platform. Extra bonus points if you link to where we can see it/get it.
My contribution: Destiny which is an anonymous, P2P, E2EE file sharing app - its basically a GUI for a Magic Wormhole implementation. Works on Linux (tarball or appimage), Win, Mac, Android (inc f-droid) and iOS. Only downside is it’s not been updated for 2 years.
Greenshot is free, open-source, and the built-in image editor is perfect (for my use-case, ymmv). ShareX is also FOSS but more well-known.
I used to use Greenshot but switched over to Flameshot. Also Free software, but has better and easier editing tools. The numbered arrows are so handy.