Has anyone ever had the feeling that they should tackle something strange...

Several times, over a pint of beer at London.pm meetings. This is, to my mind, one of the interesting side effects of Perl Monger socials.

This is the origin of Acme::Magpie and probably a few other modules in the Acme:: namespace.

I remember some discussion sbout putting together a gnu style operating system on top of Parrot.

Back to your original question, in my case, a version control system in pure Perl. Granted, this was before CL released SVK.