For basicly all automation, creating gui apps and much more. The sky is the limit with python. I love python.
I haven't used it in a while. You can do most everything in it except for GUI applications etc. I don't like it for the main reason of it doesn't work on all platforms. It is limited to whatever has a shell and some software.
I don't know this language that well. I have just made a repo with community scripts in it for redirecting bad none privacy respecting links to better ones. It's very cool.
I use MD rarely because I don't like the amount of versions it has and the syntax if italics and bold I really don't like. It simply isn't the best. I do like using it sometimes though git repositories.
Org is a special language. You can do so much with it. It's readable, it's beatifule and makes my life better.
HTML I like using for some of my website pages. Though for blogs it's easier to use ORG to HTML. Obviously using CSS with HTML for styling on all pages.