No need to tell me, whenever I'm working with Common Lisp I usually have the GNU Common Lisp documentation open to the side (it's in Info format, which Emacs has pretty good support for). I also really appreciate Perl for the `perldoc' command, which works well with the Perl community's penchant for well-written documentation (e.g. the documentation for List::Util https://metacpan.org/pod/List::Util).

Although I will admit that I was poking fun at the 'improve docs: @@ an awesome project' shenanigans from the T-shirt days.