As rattles go I'd have to say the shakey egg is undoubtedly the most versatile; the trick being to hold it in cupped hands, opening & closing to vary the tone & volume; hard (boiled) or else free (range) - the rhythmic possibilities are endless.

Mine own was gifted to me several Easters ago, since which time it has resided in a yellow wire spiral IKEA egg-cup, for which, I fear, it is rather too small.

Shame they don't come in different sizes, or even species; a shakey wren's egg would be nice, likewise a King Penguin (Penguin Eggs anyone?).

So there's a marketing idea for anyone with initiative to pull it off: authentically painted life-size shakey plastic birds eggs to flog around the festivals to families of ornithologically inclined folkies.