I see that one can't vote more than one option and hence I voted "other". If not, I also would have been voted "Baiji", the most recent of these extinctions, and for that one of the saddest ones for me as we lived the moment when it happened, also because I'm a cetacean lover. But for recover the baiji from clonation probably we would need first to extinct the animalists and anticetacean people, that is a very growing collective.
But I voted "Other" because I would choose the woolly mamooth. A lot of attempts have been done already, and none is successful but I think is only a matter of time. Having very good soft tissues preserved from which DNA can be extracted, having a very close cousin (Indian elephant) that can be used as a fetus developer and calf nurser, having enormous extension of suitable well preserved habitat without human disturbances in Russian tundra, I think the clonation of this is only a matter of time, and soon than later the science would find the gaps that still are missing in the corrupted DNA of the preserved tissues.
Having herds of woolly mammooths roaming into Siberian tundra once we can clonate one is, however, very unlikely. Mankind would want these recontructed species to being seen only in parks/captivity.