Barring the expense to create a time machine so that dinosaur and big ivory wasn't considered "unsporting."
These days, I'd say Kudu, Gemsbok, Sable, Zebra, and the mean old Cape Buffalo. I'm against predator hunting in general, but a real seat of the pants lion hunt on foot would indeed be stellar. I'd use a .375 for everything. No canned hunting, walking around in the bush with a tracker and a canteen.
Same rifle for Alaska and bear/caribou hunting, better boots and warm clothes.
After reading about the supposed "god bear" of Kamchatka, hell I'd volunteer to hunt that with a camera.