I definitely can't imagine using an Issue Tracker not integrated into a Wiki. The non-issue Wiki pages pull everything together!
And, for a TeamWiki, having that integrated Issue Tracker is a huge benefit.
Once you integrate a Version Control System, you end up with a Software Forge.
The king of the AppWiki?
TracWiki is what I've used most, with some RedMine too.
Wow, if you want an Issue TrackerWiki with HtmlArea support, for free, you get only 8 matches: Fos Wiki, Incentive Wiki, Pm Wiki, SharePointWikiPlus, Tiki Wiki CMS-Groupware, Traction Software Team Page, TWiki, and XWiki.
and none of these give you the SubVersion integration of TracWiki!
and some of those aren't very free (e.g. free for only 5 users, etc.)