2 nights ago i made a really delicious gnocchi dish, with shrimp and leeks served in a lightly spiced shrimp stock, made from the shells of the shrimp and a few aromatics and spices. (so yummmy) I use a similar stock often as a base for sauces when I cook shrimp, whether stir-frying sauteing or whatever. It took maybe 10 minutes to make, and always adds such depth of flavor.
So i would say shrimp shells get my vote for the most under-used treasure in the kitchen, more often just tossed in the garbage, than mined for flavor.
what gets your vote?