A motor-driven Nikon F
It was very effective in a "human factors" experiment I did many years ago.

I had a regular assignment to photograph a really boring and PITA ceremony, individual shots of about 50 people getting handed class completion certificates.
Usually this was shot with a Rollei or a Graflex XL press camera, nice and quiet...
One night I decided to use the F and motor. Magically, I didn't get assigned to that one any more.

Fond memories of that sound since.