I know I'm running BIG risk of getting flamed here, but..........
I'm a bit of a traditionalist I suppose. I haven't seen ANY caliber that's been developed in the last 20 years-ish, except for the .40 S&W, that can do anything that isn't already being done. I know, I know, "but it can go x feet per second faster and get a flatter trajectory". True, but I bet the deer, elk, antelope, bad guy, or whatever you're shooting at won't know the difference. If flatter trajectory is the issue, maybe you should practice more and sample different loads.
I know the slew of new calibers has been good for the biz in general, but it's just not "tripping my trigger" so to speak. But hey, to each his own. If you like it, buy it and shoot away. As another poster mentioned, if I'm in the middle of nowhere, and there's a lot of that in Wyoming, and need ammo, I can find the "basics", as in .22, .22 Mag, .223, .243, .270, .308, .30-06, 9mm, .38/357, .40, .44, .45, you get the picture? One must also account for the general shortage of ammunition, and that makes the "core" calibers even MORE attractive, IMO. But hey, that's just me, maybe I'm too "old-fashioned". God, I never thought I'd hear myself say that
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If I had to pick a specific "worthless caliber"? Hmmmmmmm.............., probably have to go with the .25 as well, it does makes a good paperweight though. But it's better than a rock or a stick. Maybe anything that ends in WSM or WSSM also. Never been a fan of short and "plump" anything, although as I get older...............