I have recently learned to use it to create an AutoHotkey for Linux implementation (https://github.com/phil294/AHK_X11), and it's been a delightful experience. If you like programming in Go and Ruby syntax, this will be your go to language. Other than that, it bears but few surprises, which I would consider a good thing. Its major downside is its compilation time and poor IDE support. Also, you should not be afraid to search through Crystal's GitHub issues or dig into the well designed stdlib's source for more exotic use cases. However, the latter is as easily accessible as is your own code, and the community around Crystal seems quite friendly and welcoming. Contrary to sibling comments, I find it well suited for programs outside of web development as well.
And most of all, it's fast.