My nearest zoo, the Lake District Wildlife Park, used to have a very impressive reptile house, with the biggest highlight for me being the alligator snapping turtles. But today their reptile collection has shrank down to a very small handful of lizards, snakes and tortoises, many of which are kept off-show and only brought out for keeper talks. While the few reptiles they do still have include a few gems like an impressive Burmese rock python and yellow anacondas, I'd still love to see a few more reptiles added at some point. Perhaps unlikely, because a portion of the reptile house is currently being re-developed into a taxidermy display area.
Up until very recently, the Lake District Wildlife Park also kept squirrel monkeys and Asian palm civets, but both are gone now, with the old civet enclosure being re-developed for some type of bird (the keeper I was talking to couldn't remember the name).