Special is not just any Rh neg, but Rh NEGATIVE of GROUP O. People with this blood have very good health, excellent immune system and life expectancy much longer than average, all indicators being statistically significant. Moreover, Rh O blood is used to make medicines for HIV treatment (don't remember the patent number but you can find it in the database, it's not secret). Strangely, Rh neg O affected by HIV cannot be treated with the same medicine, although incidence of HIV among them, again due to excellent immune system, is very low.

Rh O's have good intuition (also easy to train, if wanted) and higher than average IQ. Their heart rate, breathing rate and blood pressure are lower. And, unlike you will commonly find on the internet, the highest percentage of Rh neg's is found not in Basque region of Spain but in 2 other different parts of the world. In one of them I was born and lived before moving to SA.
And, was part of an extensive research on blood groups. There were more interesting issues discovered, unfortunately those cannot be, and were never made public