Oh oh oh I got a good one and an OK one. First one goes back a few years
Abit Intel Mobo (forgot model back in 2003)
Fried DDR Memory Voltage Regulator... Nice poof of smoke, suprisingly it was working for a while even after it went. Overall mobo failed.
Asus P5B-Deluxe WiFi edition.. (May 2007 right when the 2900XT came out)
I know I have pics somewhere on the forums on this. Some how during my water cooling phase, it was working for a while nice and smoothly, couldn't figure it out loadded, unloaded and even turned off I was picking up residual voltage on the waterblock. When the system was off I was picking up less than a volt, and on I was picking up full 12 volts. I could not figure it out one bit. Board looked good, no contact issues, the slots where the bolts when through where totally fine.
One morning just before I was leaving for work after I was going to let the PC run all day it happened. Loud bang, flames shooting out the back side of the PC, yet the whole system was still running perfectly fine. Took a look at the damage, it blew a hole through the motherboard on one of the slots, melted the threads togeather on the bolt, charred the back of the case, smelt horrible. Basically no visible damage on the front side of the board.
This had to be my best hardware death
Right before gaming weekend (friday morning) and I had to get it replaced ASAP. No other hardware was damaged in this incident.