Brains, liver, "chitlins," tripe, heart, fish heads, snails, ramps, chicken feet, and the like are all good. Just don't make a yucky face when trying them.
One rule that my kids had growing up was that they had to take one bite of anything that was served at a meal -- and they had to keep a pleasant expression while doing so. We never had food problems. I do not recall their ever refusing to eat more than that obligatory one bite.