I think the response(s) you'll get will largely be driven by 1) where are you going? (hunting RSA for example is a good bit different than hunting Zimbabwe).. and 2) what are you hunting? (walking down an elephant in Mozambique for example is going to be very different than chasing PG in Namibia)...
For your typical RSA PG hunt, you honestly dont need much.. you'll get a variety of answers, but for the most part its really about your personal preferences and needs.. some of the things I like to carry along, others will think have no value.. and some things others like to have, I personally wouldnt carry or find any use for...
I mostly just take a small 1250 CI pack about 1/2 the size of a typical "day pack" just to keep a couple of bottles of water handy, a place to hold a few snacks, etc.. I have spare ammo on hand in the pack, a decent multi-tool, a small med kit, etc.. and its a place to put my cap and gloves and light jacket when the day gets warmer and I want to take that stuff off, etc..etc..
Truth be told, even with the things I do carry, there has never been a need for any of it (except maybe having additional ammo if its been a great day and I need to fill the rifle back up to continue hunting)... the PH always has a cooler full of water on board, a few snacks, always has an ample med kit, plenty of knives and tools if one was ever needed, etc..
I just like knowing I have a few cornerstone items on hand, and have always been a "better to have and not need... than to need and not have" kinda guy..