Those little flat semi-circular rubber things with the flat metal bit in the middle that you stick on your tongue and make a really piercing whistle* - have you ever got any use out of one of those?

Swiss Warblers - they really are the most amazing things; similar to the Punch & Judy swazzle; lots for sale on the streets on Manchester on Saturday. Oh, and I forgot to mention nose-flutes & whistling straws...