Tongue is a delicacy! You peel off the membrane with the taste buds, simmer it long and slow with pickling spices, chill well and slice. You can eat it hot or cold in sandwiches (with mustard). Some folks will chill it with the strained cooking liquid, which will form a collagen-rich aspic. It is dense and tender and delicious.
Cow lungs are also fairly good and usually made into a soup or a stew. My grandmother called it Lungen Stew. She made it with a lot of pepper and cooked it a long time as lungs are bland and chewy.
I have never had it, but even the cows tail makes a great ox tail soup...