Personally? Tapirs, zebras, maras, camels, alpacas, emus, reindeer, foxes and deer.
They have seven sections; paddocks (which I was on), small animals (red pandas etc), birds (falconry displays etc), farmyard, carnivores, primates and reptiles. Work experience people are only allowed to work in the former four, so you won't be working with the tigers or anything
They get very busy so you don't get a choice over which section you're on unfortunately. I was only there for a week and I was very happy with where I was put, but a couple of people I spoke to on farmyard were a bit disappointed. If you're there for more than one week then they let you rotate through sections, but again you don't get to pick.
As I said I think I was reasonably lucky (although I would have been equally as happy on small animals or birdies
), but it was a great placement and I'd definitely recommend it