Definitely my Abit VA6 (MVP3 Slot 1)... It would only get through POST once every 15 tries. I swapped in about 20 different memory modules, a PII, Celerons, PIII, different power supplies and cases, anything and everything I and a few others could think of, and even replaced 90% of the caps on it. Then suddenly it did boot up and run fine for almost a week, about 7 times in a row, then went back to working 1/15 again... If only it would NEVER work, i could give up.
Then there's the DLink Webcam. Sometimes works, usually won't, and the codecs for it caused other video apps to crash too. I think it has a clear case so you can better see how much it sucks.