I voted nerd. I do game a bit, but that's not really why I overclock; it's only a benefit. I overclock because it's a hobby, like getting something extra for free. It gives a sense of accomplishment, like you know what you're doing with computers 😉 .
I think overclocking is why a lot of so-called hardcore PC users upgrade, because they can get top of the line performance (or close to it) for a fraction of the price. I certainly wouldn't be upgrading every year if I had to shell out $1000 for a CPU, etc.