Inno3D & other similar low-class brands like Grandmars, HIS, Galaxy, Focus, Colorful, etc.. When my Inno3D GeForce4 Ti4200 broke down within the warranty period, I rang them up for a replacement, or at least a repair. Company was based in my city at the time, so honoring the warranty should be a breeze right? No. Staff were unhelpful, and I got passed around the office telephone system like a used tissue. Most couldn't understand basic English. In the end they hung up on me.
I then got a quick replacement 9800 from another cheapo brand, Grandmars I think. Experience was so-so, the good was that it turned out to be a Pro rather than a non-Pro. The bad was that I saw artifacts on boot, but not in Windows. Obviously a return of some kind by an idiot modder, retailer refused exchange (it was still functional) & I was stuck with it. It worked well for the next several years, so I have to give it credit.
When I bought my new system, I made damn sure all my components were from good or at least reputable brands most were familiar with. I also bought my system from a larger company, a step up from simply purchasing parts individually from small dimwit stores. These folks honors all warranty for 5 full years, even if some of the components originally had 1 or 2 years warranty on them. No extra payment, they'll handle everything for you.