I think that piranhas and sharks tend to attract visitors.
I would say Peafowl are good candidates, probably the ones that free roam.
I worked with one that would appear when someone was doing an encounter session with something like a giant millipede, and totally upstage it.Yes, particularly a displaying male. Always draws attention.
The real test is an animal that can draw a crowd even when it is doing nothing....
I wonder if an adult bull walrus would be its equal, but I have never seen one...
Ducklings. Whether wild Mallard or on a pond in an aviary, small ducklings always attract attention. In fact, having a duck species parent rearing in an aviary is a good way of people not walking past with an 'it's-only-birds-in-there' attitude. Instead, they stop and goo over the little fluffies, and just might notice the tanagers or whatever that are also in thereAnother vote for meerkats, penguins and flamingo. I also agree that small primates usually seem to be active. I really like otters, but I have mixed luck with them. I have never ever seen them at Hamerton, for example, yet have never failed to see them at Dudley.