The official SASS site has a list of possible options here: https://sass-lang.com/install
There are paid options, free options, and even open source options. These are then available on Windows, Mac, and/or Linux. They’re also inter-operable so it’s not a requirement that we use the same tool (though some consistency might be nice when it comes to sharing settings, discussing things, etc.)
I’ve personally used https://codekitapp.com (paid & Mac only; my current app of choice), and http://livereload.com (has paid options for helping further development & support, but it is provided 100% free per it being fully open source [Windows option is fully free even from the main download option]).
There’s then also http://koala-app.com (free & open source), https://prepros.io (paid), https://scout-app.io (free & open source), and others.
What’s nice is that you can really use the tool of your choice and it should play nice (I know Kaitlyn uses a different tool from me) since it’s still just