What are the confirmed superstars that zoos can build exhibit capital campaigns on?

Some of them are being phased out?

 

Several species of gazelles are on the way out (if they aren't gone already), and others are just in extremely low numbers. The only priority species currently are Speke's and slender-horned. Zoos are being encouraged to shift from plains zebras to either Hartmann's mountain or Grevy's but in some cases zebras are just dropped altogether because of aggression. Moose have never had a huge population, as far as I'm aware, due to their news for extremely fresh browse. This gets costly if it can't be locally supplied, and although many would recognize it as a moose, many would just say "deer" and move on, unless it had a particularly impressive set of antlers.

I'm not sure about the state of wildebeest, but they sure don't seem to be growing in population size. I could be wrong, any input would be appreciated

 

@jayjds2: Also Addra, Cuvier's, and Soemmerring's gazelles. Unless something has changed recently, the only gazelles being phased out exist in numbers less than 10, or have indeed disappeared. Pretty much right on your other points.

Wildebeest enjoy a sizeable population with a positive growth rate, and several institutions hold herds of them.