Freaking everything. Oh wait... you probably wanted something more specific.
Kudu will always be on the list for me, for every subsequent trip I still hope to make. They were the first thing I ever wanted, back in college, and I have 3 so far. I'll take as many more as I can get.
Warthog have seriously grown on me since my first trip. Ditto what I said about kudu.
Two cow buff down, and I REALLY want a bull. I'd say they'd be an every time thing I would want but that might get expensive, and I have other stuff I want to hunt too.
It is true also that species I haven't hunted will draw me back. Two that have REALLY grown on me since my first trip are crocodile and hippo. I have hunted neither so far, and hope to change that in the years to come.
And reading the recent lion threads, I want to hunt lion. A male lion. I have reached out to one sponsor here and may chat up another one soon. I fall into the camp of I'm good with it done right with a reputable outfitter, and I worry the window is going to close, so I need to piss or get off the pot. I had said once I wouldn't want to hunt lion because I do not find returning home without the trophy palatable. I am moving past those sentiments. A truly wild lion in a truly wild place would be wonderful, but that's never going to be within my financial reach, not if I want to hunt other stuff too, both here at home and over there.