Nduja is the best sausage in the world. Can be used in anything from soups, to sauces, spreads, pizzas, condiments, stuffings, marinades - the lot.
It varies in spiciness & is quite a rare delicacy outside of Italy but becoming more and more popular. Lots of pizzerias etc get it shipped in for use as an ingredient but I'm well-versed in using it for home cooking now.