IBM, 3dfx and Yamaha for obvious reasons.
Well, Yamaha might not be so obvious, their only computer parts I know of are a few sound cards/chips. But those few are definitely awesome. What am I saying.. everything Yamaha makes is awesome.
Hewlett-Packard is also one of my favourites, since my first 486, was a Hewlett Packard. The monitor from that system still heats our house to this very day. (though I hate that stupid officejet printer)
Philips is another one. Like Yamaha, they never made many PC parts. Unlike Yamaha, their quality level is not always consistent. But the few Philips parts I own are good enough to call them my favourites.
For example, I have a pair of Philips PC speakers. They're not very loud and sound like crap, but are still the best sounding computer speakers I ever heard.
The screen I'm staring at right now is also made by Philips. It's a standard shadow-mask screen, sharp enough but still a bit on the blurry side, with a flat lens in front of the obviously round tube. But the amazing colours and contrast make me want to stare at it all day 🤣
Now if there's one brand I don't like at all.. it has to be Creative. The only good thing they ever made was this commercial. Ironic is that their sound cards work exactly the other way around: first impressions are good, but after a while you'll come to the conclusion that it is actually a piece of trash. 🤣
Oh and before I forget, IBM is awesome.