#FreeSoftwareAdvent day 11: Dokuwiki
I use Dokuwiki a lot. I have a private wiki for personal notes, my business has a private wiki for documentation, I maintain an RPG website that is a wiki, and there are others. I even write my books in a modified Dokuwiki.
I particularly like that pages are stored as plain text files. On some of my wikis, I've taken advantage of that by writing bash scripts to check or edit files.