Markup languages

So, /prog/. You are writing an application, and want to let users write in text with some basic formatting. Which markup language do you use?

I don't think the end-users are SATORI enough for teh S-exxxpressionz yet. So let's get down and serious;
There's BBCode, of course, but that smacks even more of web development than HTML does. A HTML subset might actually work okay, everybody knows some HTML, right?
There's also a gazillion different Wiki-markups, like Creole and WikiMedia markup.
reStructuredText looks nicer than the Wikis, but seems to be very FIOC-specific.
Or should I just let them attach a .docx document, or give them a WYSIWYG editor (faggot)? It's all your call.

Markdown is nice if people want to learn it. HTML or BBCode is easiest for forums, since people know it. Regular users like WYSIWYG editors.