We have many versions of meatballs. You can use leftover cooked meat instead of raw meat for an even tastier version! Leftover roast beef or brisket are great! You can add 4 tablespoons of very finely chopped olives for a different flavor. You can add leftover cooked spinach, drained well and chopped (in this case decrease the amount of the bread/broth mixture). You can add plumped currants and pine nuts, and end the cooking with some lemon juice, for a sweet-and-sour Sephardic touch. Also try substituting mashed potatoes for the bread/broth mixture.
Try them all!