I have seen a lot of rare species and some of them luckily last year with first visits in Antwerp, Rotterdam, Planckendael, Singapore Zoo and Night Safari. But there are some animals, which I would like to see, but haven´t seen yet: Northern White Rhino; Sumatran Rhino;
Javan Rhino; Giant forest hog; Chaccoan peccary; Hirola; Mountain Nyala;
Walia ibex; Philippine eagle; Giant sable antelope; Iberian lynx; Mountain Tapir; Siemen Wolf; Kakapo; Massai Giraffe; Cape mountain Zebra; Tamaraw; Kouprey; Californian Condor; Pygmy ant-eater; Giant armadillo;
three-toed sloth; Dugong
I've seen some of these:
Northern white rhino, Masai giraffe and giant armadillo (London)
Sumatran rhino (Port Lympne, Bronx)
Philippine eagle (Planckendael)
Giant sable antelope, mountain tapir (Los Angeles)
I would like to see many of the animals in these lists, but I doubt if I'll ever see some of them.