Wouldn't particularly say that I have specific brand I'm 100% loyal to, I accept that most companies at some point will mess up. But I do have a few go-to brands for certain parts that have gained notoriety from the public and that I trust based on personal experiences with them. None of these are set in stone, and are bound to change eventually.
MoBo: MSi and ASUS right behind, though I will say that as a previous MSi X570, they really dropped the ball on the lower end X570 boards. Found it hard to think they dropped the ball this hard on the X570s.
CPU: If Intel does what is best for its consumers, and it fits my needs, I'll take it. Vice versa for AMD.
CPU Cooler: I haven't used anything other than Hyper 212. I've been really looking into Dark Rock and maybe Noctua for Air Coolers recently. Arctic for an AIO.
GPU: EVGA, without a doubt. Have heard overwhelming positive remarks about their cards from reviews, plenty of friends, and of course I've had nothing negative in regards to their cards. Outside of what had happened with the ACX 3.0 in the GTX 10XX series that burned up, they've been one of the most solid AIB partners for Graphics Cards. I'm open to MSi and Gigabyte too, but EVGA takes the cake for this one easily.
RAM: Being a Ryzen Owner, the past 3-ish years, I'm going G.Skill easily. But since RAM doesn't really go bad or rarely does, it hardly matters. I'd go Corsair, Crucial or hell, even HyperX.
HDD: I am definitely in the minority here, but Seagate drives have never failed me, and both in my current system 2 & 8TB 7200RPM are Seagate Drives. I've had 4 WDs in my lifetime, all have failed me within a year. So I'm definitely on the Seagate end of this.
SSD: The most popular is Samsung, and that's for good reason. But that isn't to say that there aren't any other good ones. Plenty of high quality brands that are much lesser known than Samsung.
Case: I don't have a go-to brand. Currently an owner of a Corsair, but I have my eyes on my next upgrade being either a Lian-Li, NZXT or Phantek Mid-ATX.
Mouse: I've been a Steelseries guy for a number of years, especially the Rival 300 being a mouse large enough for my hands. Logitech and Razer as well are 2 I'm looking into, and have heard great things about for a while now.
Keyboards: Outside of self-building a keyboard, which I am in no position to drop so much money into. I'm quite certain after spending hours at a Best Buy trying out different keyboards. I'm a Corsair guy for sure; these keyboards are really durable. Love my current K95 RGB Platinum MX Speed switches. Not without complaints for a while though, until they released the recent version that comes with PBT keycaps. May try a Ducky one day. Open to self building one.
Headset: Don't really believe too much in gamer branded headsets, having spent a lot of time trying other headsets at a local Microcenter. But I've been the owner of a HyperX Cloud II for close to 3+ years now and it's something I have no regrets about. I have heard some good things about Corsair as of late though. so these two may be the only "Gamer" brands I trust. Looking towards a Philips, Audio Technica, or Sennheiser as my next upgrade.
Monitor: It could be anything. As long as it provides 144hz+ Freesync/G-Sync compatibility, at least 24" 1080p and above, with adjustable height and tilt on the stand at a reasonable price.
PSU: If it works, it works. As long as it's 80+ rated, preferably Gold or above I'll research its reliability and give it a go.