My question must be: worthless for what?
I will skip on the vote for now. There are more than a couple of cartridges on the list I am not fond of, and probably never buy, but who am I to rain on someone elses sunshine. A couple of examples are:
I shot my first elk with a 32 Win Special, it really was a rotten choice of rifles for the task almost 250 yds, and a 600+ lb animal. It took three shots to down, first a heart lung shot, second a heart shot and the final a spine shot. All of these shots were well placed and with a more suitable rifle such as a 30-06 the last 2 shots were probably unneccesary. But the 32 was what I owned and it worked, ideal candidate for the task at hand....hardly.
Another of your losers is the 30 cal carbine, I have owned one of these in the past, never used it on game, and the carbine the round is chambered for is certainly not a hunting rifle. But for all its shortcomings, the M1 clone had one of the highest fun factors of any rifle I ever owned, simply it was a blast to shoot. If I was going to hunt with the 30 cal carbine, I would insist on a single action or bolt gun. This on small game at reasonable distances would work not ideal certainly and I wouldn't bother making a rifle in this, but it would work.
A couple of your choices boggle my mind that they are even on the list, 257 Rob, 6mm Rem, 338 Win Mag, maybe you don't like these, but all three are excellent cartridges. For instance if your hunt in the Southwest a 257 Rob or a 6mm Remington are both excellent all around calibers, and the varmit hunting guys love the 6mm Rem. A 338 Win Mag is a very common choice of rifles in Alaska, Canada, Montana for larger game animals, and is used extensively on plains game in Africa. Your text inclusion of the 375H&H must be a joke,
I frequent another hunting board with a lot of African and Alaskan hunters and the storm that statement would have made on that board would take you years to live down.
My current list would look more like:
401 Winchester
351 Winchester
.220 Weatherby Rocket
8x50R Lebel
8x56R Hungarian Mannlicher (.329" bullets)
32-20 winchester
.256 Winchester Magnum
I admit I am not a big fan of .223 rifles, too light for deer hunting, better options of varmit hunting, in mine mind a caliber that has no reason for existance, but it has a huge following and it would be absurd on my part to consider it useless. There are a lot of varmit hunters and match shooters that would slap me ( rightfully ) if I even suggested it.
And remember some of your usless rounds need to put into historical perspective ( mine too ), the 8mm Lebel made a lot of sense when it was introduced it was the most modern cartridge in the world. Now its an oddball rimmed 8mm, with not impressive ballistics, chambered in crappy french milsurp rifles, that is further hampered by Berdan primed brass. But in 1886 this rifle and caliber made a lot of sense, and the rest of the world were reeling to catch up......times change so do perspectives.