I made this little brass whistle for my Grandson from Walter Yetman's article in the Oct/Nov issue of MW magazine. I made it an inch longer and changed the slide handle shape a bit. To add a personal touch, I engraved a nameplate on my little CNC router and soldered it on. It cleanly whistles with very little effort and has a full octave range.
Probably not as much fun as the popgun I made him last year but I think he'll like it OK. It's noisy and he'll be able to drive his mom nuts with it too.