On this note, I want to make a correction. Previously I stated that the "Australian Reticulated Whip Ray" would be the species on exhibit. Going through some photos I took, it's actually the Leopard Whipray (Himantura leoparda) which now thinking about it, makes a lot more sense because she (it is a female individual) was coming from I believe Ocean Park Hong Kong or an aquarium in Japan where they are on display (the last time it was mentioned was over a year ago so it's a little foggy). There weren't any clear upclose photos of her before seeing the signage so I assumed it was Himantura uarnak which is much more common. I believe this makes her one of the few H. leoparda in America, I can't find any photos or records on here about one in an American aquarium (besides Georgia since they have a profile on the species from 2018 but doesn't specify if they have one in collection right now). So that's a really neat rare species I wasn't expecting.
Edit: I'm just going off the signage that's uploaded already, it's labeled as H. Leoparda but it sounds like the species within the genus are really difficult to tell apart but from where it came from, I'm going to assume it correct
Other rarities off the top of my head are the female Bowmouth Guitarfish (I think 1 of 2 on the West Coast since I had no idea Shark Reef at Mandalay Bay had one until going through recent media on here), I'm hoping for Leafy Seadragons but most likely they'll be Weedy Seadragons which aren't as rare, Flamboyant Cuttlefish are arguably not that rare, some of the smaller reef fish species are pretty uncommon like the Pompano. I'm very interested to see what the species debut for the Non-Photosynthetic tanks will be. Hoping for some Sacura sp. Anthias, Odontanthias sp. Anthias, deepwater Butterflies, Angels, etc that are all rare in most public aquariums.