Aside from the ETL stuff I mentioned, we also use Cygwin for the X server (although we're phasing that out in favor of something more multi-user friendly like X

Aside from the ETL stuff I mentioned, we also use Cygwin for the X server (although we're phasing that out in favor of something more multi-user friendly like X2Go) and for Unix tooling that hasn't been ported to Windows (mostly bioinformatics stuff, and which is becoming less and less of an issue).