PHP and JS in the largest project. C# in small GUIs. The gui builder saves so much time and I think they could find any reasonable developer to replace me. If I use too much F# they would have a hard time finding someone.

I also use a lot of SQL I think it's fantastic for data manipulation. There are some legacy Java apps as well.

I don't mind working with most languages (the only exception is Perl, I'm not a fan). I just love working with F#, so much less boilerplate and type safety. It's so much more fun.

But I want everything I do to last that means reducing the number of dependencies and build tools I introduce. Fable is amazing but a SAFE stack app will bring in a huge number of extra dependencies and I'm not sure what maintenance would be like in 10 years. As it is I'm working with a stack of docker containers that compile an old version of PHP and drag in legacy libraries.