I really like Dokuwiki. I remember looking at it many years ago (even then, there were way too many wikis) but for some reason my company or project at the time didn’t choose it. Maybe this was the company that decided Sharepoint was better, I don’t remember. (They never did understand why a collection of Word documents was inferior to a wiki.)
I’ve been using it for a while now, and of all the wikis I’ve used, which are quite a few, it is easily the nicest. It has such nice conventions—once you learn what they are, and use them to your advantage, everything gets so easy. Example: being able to name pages with [[brackets in the flow of text]]. And there are many more things; I don’t want to start any heated debates about it, but in my opinion, it hits exactly the right balance between simplicity and power.