In Brazil (and Latin America) I love seeing zoos exhibit any of the many unusual or diverse native species. The Xenartha is an interesting group and anteaters, sloths and armadillos are always intriguing, New world primates too such as muriquis, marmosets and tamarins are fascinating in their astounding diversity and some of the smaller and more obscure small felines such as pampas / pantanal cat, Geoffrey's cat and oncilla are treats to see.
Then there are the birds (mainly the psittacines) , amphibians and reptiles (particularly the venomous snakes) are also highlights for me. But if I'm honest (despite being a supporter of good zoos) I would much rather observe any of these species in wild areas than in captive environments and when I get the chance I often do in National parks.
When I travel outside of Latin America I'm not so interested in seeing neotropical species and actually I like to visit zoos which showcase the smaller, endangered and unusual or more endangered mammal species that are not commonly kept in Latin America. If only to get a visual reference see what these creatures actually look like in the flesh.
Some of these species that I remember being fascinated viewing would be animals like the Malagasy giant jumping rats , pottos , Rodriguez fruitbats , loris , galago , fossa , boki boky etc.