I wouldn't hesitate with the rocky mountain oysters, but that duck egg thing is just plain gross. (I had to Google "balut", and not sure that was wise this early in the morning...)
Suppose it's whatever you grow up with...
Apparently in some places, the un-laid 'immature' eggs from a hen are a high delicacy as well. I've butchered a few laying hens, and it's pretty interesting to see... but I don't think I'd want to eat them!