Most document formats don't play terribly well with source control. Almost everything you list is either effectively a binary format or convoluted markup that won't diff well. As long as you just want versions of documents and don't care about the diff, use whatever format you like. I prefer Microsoft Word documents because you can use the built-in change tracking and comment system to track deltas between documents.
As for what documents to store, I would recommend storing anything you'll have a use for later. What documents could be used by someone to continue the project should you leave? What documents would be helpful to bring a new person up to speed? This means specifications, but not documents like burndown charts.
To answer the wiki part of your question, check out DokuWiki. It stores everything in text files so they would be very easy to add into a source control system.
