http://lmgtfy.com/?q=Which+Blood+Type+Is+the+'universal+donor' Is it really that hard to do a Google search?
LOL, that was my thought yesterday but did not post. BTW, my Dad was an O Negative/Universal Donor. He would get emergency calls from the Red Cross in the middle of the night to go donate blood. One time, a child was severely injured in a car accident and he donated a quart twice in three days. Unfortunately, the child did not make it and my Dad said that he got a cold from that effort that he could not shake for a month. I believe that he stopped counting after he got his "Four Gallon" card from the Red Cross.
I just find it mind boggling that they would rather start a pointless thread here than just do a simple Google search. A big high five to your dad for his effort though.
O negative blood group are called universal donors, and those with type AB positive blood are called universal recipients.