Leave one on your deckchair when not using it. Works better than a towel to keep Germans away. Very handy for pinning reminder messages to. One prickle will winkle out shellfish.
In greece whre i live, we eat them. or rather my wife who is Greek does... Open up underneath, clean out loose bits, squeeze some lemon juice inside, add olive oil and eat the orangy bits inside. (Yuk!!) i think if you leave them to dry prickles will fall of and shell can make quite nice ornament ,although fragile.