Have a look at TiddlyWiki. I think it has the best combination of features I've seen in any wiki. (For "pages" below, read "items" since TiddlyWiki is a single-page wiki. But I think these features should apply to wikis with pages too):
- List of all "missing" pages (WikiWords with no page)
- List of orphaned pages (pages with no links to them)
- Most formatting is done by editing wiki pages
- You can't screw up formatting, because there's a default if you delete your custom formatting
- You can tag pages
- You can include a page in another page
And plenty more that I haven't mentioned. I think the formatting is possibly the best of many good features, because it's so easy to edit and so hard to screw up.
