One place I really would like to visit in Ethiopia is the Omo Valley. There are many tribes living there who are truly unique. Nomads, cattle herders, with traditions that are so different from anywhere else.
An example is the Hamer people in the Southern Omo Valley. They are not many, a little over 40 000 and they are semi-nomadic. Since cattle is the most important thing to them, they make sure their cattle has enough pasture to graze. When this runs low, they simply up and go! Building a new village wherever they find good pasture grounds, staying there until this is exhausted. Usually a village is made up of some 20 huts, plus pens for the goats and cattle.
Even the initiation to become a man for the Hamer people involve cattle. A young man has to run across the backs of a row of cattle four times, naked, before he will be called a man and be able to marry. (If he falls down, he could be given a chance at another occasion.)
There are many tours operating to the Omo Valley, it is becoming a very popular place with tourists. The nature and wildlife down south is also very impressive, with hippos, crocodiles and an impressive birdlife.
At times the Omo Valley is not recommended for travelling because of tribal fighting, so it is good to check with the embassy before planning anything!