Ask HN: What shell do you use, if not *sh?

I don't know bash. I don't want to know bash, I am not interested in a language that uses the program [ for if-branches. (Also I don't want pitfalls in the simplest possible tasks, thank you very much.)

I am looking for a shell language, with the following criteria:

    - fairly popular and alive
    - is small, like putting a binary in the /bin folder 
    - can start programs, support pipes, file operations 
    - has variables, if branches, lists, for loops, basic integer arithmetic, strings 
    - not POSIX compatible, or resembling to bash 

Google offers a handful of options, but I am interested if people actually use not bash or bash alike languages for shell scripting.