I can second that. It is actually beyond amazing, and I'm not one to say that lightly. Not only it does screenshots, but it has editable annotations, records gifs or videos, has complete keyboard support, and uses only 5MB RAM.

As well as having a bunch of useful tools for people working with screens, such as ruler, color picker, and a QR reader.

I'm really happy with that.

It can things I didn't know I would like to have :D

Yes, and it's a recurring theme. In Portuguese we have a word "esmero", which is very applicable. It means something made with extreme care and craftsmanship.

For example, I once needed to take a very precise crop off a screenshot, and thought "it would be nice if there was a way of fine tuning the mouse position". My first thought was somehow using the arrow keys, I pressed one of them and voila! The mouse moved a single pixel in that direction.

It's hard to pinpoint in specific features, but the best description is that ShareX is a very well laid out workshop, with everything within reach and nothing in the way.