AB- worldwide.
And in HK, only 0.5% of the entire chinese population have a (-) blood group.
2007-11-30 17:59:30 補充:
If you say "precious" (珍貴) in terms of the medical value, then I agree with the person above that it is O-, because O- blood can be given to any other person, and a person with O- blood is called "the universal donor".