There are a couple examples in ethno-American cusines. Here in the States, most authentic Mexican food connoisseurs have probably had beef tongue (Lengua) or beef head (Cabeza) tacos. If you have ever celebrated Pascha (Easter) with a Greek friend, you probably had Magiritsa which is a soup made with lamb entrails (if you have hung out with Greeks period, they tend to eat the whole lamb...all of it) And if you have had some traditional South American soups or dishes, a lot of them are made with livers (beef, pork, or chicken). Something else that is becoming a trend lately in some hipster restaurants is sweetbreads.