What type of problems do you solve using Lisp?

Hello! Let us have another Friday social topic.

What type of problems do you solve using Lisp? Please share these details while answering:

• Which dialect of Lisp do you use?
• What problems do you solve?
• Why do you choose Lisp to solve these problems?

I have a feeling that this thread might get inundated with too many Emacs Lisp posts about solving personal productivity problems. That's fine. But I suggest posting stuff about other dialects of Lisp too. The more dialects of Lisp (CL, Clojure, Racket, etc.) are discussed here, the better! We want to have a good variety of answers on this thread.