I have a much smaller list of rifles I've seen used by PHs personally, but the these two I can say for sure and have seen in the hands of the PHs, I won't put the names down as you never know who doesn't want their info shared especially when it comes to firearms stuff:
-Zimbabwe Buffalo / PG hunt: .458 Lott controlled round feed. Also has a .375 H&H stainless Model 70 .375 H&H
-RSA Plains Game: .458 Winchester Zastava Mauser with upgraded stock, and sights.
So .458's controlled round feed bolt actions have ruled in my experience, and one .375, which incidentally just happened to be the rifle the PH was carrying the likely saved his life not long after I left. Was the first really bad charge he'd had, and he happened to pic the .375 that day, I'm sure he would have preferred the .458 but the .375 worked.
Will see what they're carrying on February's Lion hunt.