The last computer I built was designed specifically for gaming purposes, I spent months upon months simply figuring out which parts to use. It was the motherboard which gave me the most trouble, since I wanted a full form ATX motherboard with 2x PCI-E x16 slots for multiple GPUs and at least 2x regular PCI slots for other expansion cards there were hardly any motherboards meeting all of these requirements.
Once I had everything selected I began with my usually solitary and normally meditative state associated with participating in a particularly enjoyable hobby with no disturbances. I cleaned out my case; removing all of the drive bay covers and expansion slot covers which would be in my way, installing all of the motherboard standoffs, installing the power supply, and clipping all of the rogue wires to the side so they aren't in the way of anything.
While installing the CPU (an AMD Phenom X3) I accidentally put pressure on the CPU heat spreader instead of just letting the chip fall into place. This severely unfavorable action resulted in the bending of several pins on the CPU. It was a very meticulous process to bend those pins relatively straight again so I could install my CPU and see if it was toast or not. Turns out it booted up without any hitches, everything else went into place very easily and the system turned out great. I got the CPU overclocked to 3.0Ghz, there were dual Radeon HD 3870s, over 2Tb of disk space and 8Gbs of RAM. I built this computer about a year ago so it's already obsolete yet it still dominates over many desktops you see for sale in Best Buy.