My fourth version of wiki was a dramatic simplification into functional cgi scripts for show, edit, save, search and any other function that might be added.
I've cast a number of projects as specialized versions of wiki. Typically this means writing instructions for my self and others. I often write a cgi script or two to do something interesting with data available in the wiki pages.
IRLP Wiki provides wire-line control of my IRLP radio node.
International Dinner Wiki for coordinating and remembering our regular pot-luck dinners.