I am visiting Hamburg next week. Any zoo chatters visited recently and can tell me of any rare species I should look for or any must sees.
Zootierliste mentions the 'bearded ghoul', a relative of the stonefish and the Hamburger, a breed of domestic chicken. The zoo also has Pacific walrus, Kittlitz's plover and white-spotted guitarfish.
I would also mention the red-billed oxpeckers. And maybe the chestnut-backed sparrow larks (they have the only ones in Europe according to Zootierliste, but I don't know if they are interesting to anyone but bird enthusiasts, while oxpeckers at least are quite iconic due to nature documentaries). There are also some rare bird species flee-flying in the Tropenaquarium. Unfortunately, I only managed to see the two species of bee-eaters, bearded barbets, Livingstone's turacos and golden-breasted starlings when I visited, so the others may not be easy to spot.