Our LAN group has the quintessential That Guy.
It's very common that someone's computer starts acting up, and won't run/install the game properly. Along comes That Guy, who will fix the registry files, change some settings in the .msi file with a hex editor, and do some other voodoo magic, until everyone's finally in the game. After that, he owns the shit out of us for a solid two hours.
I myself am like Almost That Guy. I'm slightly better at most games than other people we play with, partly because I'm a geek, and other people have lives. I'm not uber, but when we play, I usually get some 4:1 k/d ratio. Compared to That Guy's 15:1, and other people's 0.5:1 to 2:1