Well, I'll chime in with mine.
1. Valdyan, of course. I'm not nearly fluent enough, and I'd like to
speak it in the role-playing game at least. I don't expect my players
to be fluent as well :-)
2. Denden; not only to speak it with Boudewijn, but also because it's
a really gorgeous language.
3. Drasele'q. I just like it!
4. Teonaht, partly for the same reasons as Doug, partly b