I think once you get past a few national governments, there’s no middle sized thermonuclear device manufacturing. I suppose there might be a few mom-and-pop operations, but really you’d have to go to one of these nation-states if you’re looking to buy.
Automobiles … once past the first layer or two, your options really shrink. This used to be the poster child of economies-of-scale, perhaps not as much anymore.
What does large mean, like 747 size? Mentioned in the OP, but I would’ve mentioned Bombardier Aerospace for commercial-sized, unless we are only counting US companies? They have half as many employees as Airbus, so not tiny (that may not be the best metric). Alaska Airlines likes their planes I believe. Also Embraer, although I haven’t really heard of them until just now.
Does e.g. Lenovo make their own hard drives, or are they just branded? LaCie? Some brands also may specialize in internal vs. external drives.
I would argue that despite competitors, customers effectively only have a choice between Intel and AMD for CPUs, or Nvidia and ATI/AMD for video cards. You can buy one of the third party ones, but you’ll probably regret it.
There’s plenty of charts online like this or this.
Most of the external/portable hard drive brands will be a case made by someone like LaCie, but the drive inside was made by someone like Western Digital. Sometimes the official specs will tell you the HDD brand, but you can always tell if you crack the case open.
Oh, I’m sure there is rebranding going on. But these companies also make or “make” internal drives. On Newegg, LaCie has 22 3.5" internal drives listed, and Lenovo has 100. In that case, they probably hide it better.
The thing about all these examples is that the world is more efficient with fewer players, in most cases.
Virtually all of these examples are for a product that requires either advanced technology or massive infrastructure to compete in the marketplace. The fewer the companies there are, the fewer duplicate functions “the world” has to pay for. There’s a massive prototyping lab staffed by a bunch of engineers and scientists for the hard drive companies, food manufacturing is done is gigantic mostly automated plants, and so on.
That’s why there are so many zipper manufacturers left over : it’s apparently only moderately difficult to manufacture zippers.
Natural monopolies like a city electric distributor; or a government contractor for, say, printing legal tender; or those involved with regulated technologies, like weapons.
The CFL? Nowhere near as popular, and the rules are slightly different. But nothing too major, just well known things like the number of downs, as well as lesser known rules like having to say “sorry” every play. And players can switch pretty easily. Not much coverage in the US (although sportsbooks cover it), but both are popular up north (let’s pretend that’s not relative to hockey).
I was going to mention “Sporting firearms”, actually - there’s just not that many firms globally who manufacture guns for the civilian market and they’re all generally pretty well known (There’s countless more who modify or customise already extant guns, however).
I had once heard that even though their are dozens and dozens of brand names on microwave ovens that there are only a couple makers of the magnetrons inside them.