There is something I saw on the wild here https://github.com/Shinmera/legit/blob/master/repository.lis... which I thought was pretty cool.

We all know about memoize, but let's say I want to define a global hash-map, where the keys are actual pieces of code and the value the result that would be evaluated when executed. Something like this:

  | Key                        | Value                          |
  |----------------------------+--------------------------------|
  | "hello"                    | "hello"                        |
  | (square 5)                 | 25                             |
  | (factorial 5)              | 120                            |
  | (git-tags "~/foo")         | (list "1.0.0" "0.1.0" "0.0.1") |
  | (make-instance 'singleton) | #<SINGLETON {1301DE5A03}>      |

Which can then be used like this in a trivial way, just passing code because code is data:

  (let ((path "~/foo")
        (tags (cache `(git-tags ,path))))
    (format t "Tags of ~a~% ~{- ~a~%~}"
            path tags))

Sure, something like this is possible in other languages, but having done macros in languages such as Rust and Nim, it involves such a verbose and syntax soupy way of dealing with the AST that I don't feel like reaching for those abstractions that often. I'd rather just write boring code, and most consider this a feature.