Four items stand out for me:
Asus Striker II Extreme motherboard: The most unstable board I've ever owned. I'd swear the BIOS was a sadist, and whenever it detected I was happy with the system, it would just throw a fault at me at random.
Intel Core Extreme X6800: It might have just been disappointing compared with the budget offerings (E6600 particularly). Factor in the $1K+ price, and it had me searching for the suicide hotline number.
Nvidia GeForce FX 5900 Ultra (Gainward Golden Sample): I was told this was an enthusiasts graphics card. They lied.
ATI 3D Rage Pro Turbo: Spent some cash and supposedly Upgraded my 3D Rage Pro (Asus V264GTE). Turned out I spent more money to get the same card I already had. By the time ATI had wrung some extra performance out of it via driver, the next architecture was out.
1)Your disappointment in the x6800 is very much ,a shared experience,I rma'd mine cause I was sure there was something wrong with it.lol .turns out, no ,we were duped , guys were beatin me up with e6300's on decent boards..later bought the QX6850,DUH,! still have both..
2) Pentium D 840 Extreme Edition. speaks for itself.
3) the Ageia PhysX card by BFG tech,we know what happened to that..was cool at the time..
4)Vox usb,tv tuner card. returned several before I got my money back , junk..
5) most Seagate HD's I bought were or are junk..several failed models now ,out of warranty..thought they buying Maxtor would have helped ,now Maxtor Shite too.I have 2 x 6 gig Quantum Bigfoot HD still work great.they don't build them like that anymore .lol.
6) upgraded an Geforce fx 5200 to an FX 5500. later found out was just a bios flash to get the 5500..
7)2 X GeForce FX 6800 ultra 512meg,preordered for the extravagant price of 1299.00 each Canadian,not so bad, took over a month , had them 4 days when 7800gtx was announced and on shelves ,ending paper launches,LIES!
This maybe. should be first on my list,speaking of OEM,, my IBM Aptiva E3N personal computer,with an AMD K6 II 266/300 ,windows 98,for upwards 3000.00. had to upgrade it from day 1, found a pci Radeon 32 meg AIW in a pawnshop for a 100 bucks ,a steal as it was retail .still a 300.00 card.