Do any WYSIWYG editors exist that work natively in Markdown? (any Platform/Language) ...So consumers don't have to see the code behind, just work in an MS-Word like interface.
An assisted MarkDown editor where you're viewing and editing the Markdown-source (like the one I'm writing this question with) would also be okay.
There is the Wysiwym Markdown Editor (The one we're using here). It shows live-markdown though, rather than masking it. I think the great thing about Markdown is that just about anybody can understand the basics of it.
This is the only editor I know of. After doing a cursory browsing of Google it appears to be one of the few, if not the only one in wide-spread use at the moment.
A large list of Markdown implementations at the Markdown Wiki.
And: