Nose Flute

A truly unique instrument(?) that's fun for any age.
The flute is held over your nose and mouth (see 2nd pic below), you blow it through your nose (it's not as bad as it sounds from the description...).
Your open mouth becomes the "sound chamber" - as you open and close your mouth, the pitch of the note changes.

The sound of the Nose Flute is reminiscent of a Slide Whistle, but is still very unique.
With some practice, it is quite possible to play tunes on it. As with many other wind instruments, it can also probably be improved by some "tweaking".
For instance, on one we were playing with here, we used some Scotch tape to narrow the air opening and to focus the wind-stream to sweeten the tone and cut down a bit on the air requirements.