Frankly, meatballs are almost always eaten from a sauce, tomato or sour cream. So I find an all-purpose meatball works just fine. This recipe makes a lot of them, and they can be frozen for use when needed. There is also a technique here that I got from Alton Brown.
Lightly mix the meats,onion, and breadcrumbs together. Don't overwork.
In a bowl lightly beat egg and add the seasonings. Then add to meat mixture and gently mix by hand.Add milk and mix until mixture is loose enough to easily work with (sticks together) but not sloppy wet. Use as much of the milk as you need.
With a small ice-cream scoop, measure out meatballs in approximately 1" size, or smaller if you wish to have them on hand for meatball appetizers
Place them on: 2 jelly roll pans lined with parchment and with wire racks on top. Place them close together on the wire racks but not touching. The racks allow any grease to run off and the meat doesn't burn on the bottom. They cook evenly this way.
When you have them all done, place into a preheated 400 oven for 20-30 min.
Remove and cool on the racks. Place in freezer bag and pop in the freezer. Take out as needed for spaghetti or Swedish meatballs or Meatball sandwiches. Just thaw and place in your sauce and heat up.