Noun. - A nerd who is only interested in a very well-defined sub-subset of nerd culture. While nerds are generally believed to like comics, video games, D&D, sci-fi, anime and astrophysics all at the same time, the niche nerd enjoys one or two things and tends to ignore or downright repudiate the rest.
As a niche nerd of extremely refined taste, I find your proposition of going to Comic-Con downright laughable.
Don't bother trying to buy Mick a video game for his birthday; he only likes Japanese RPG's for the Playstation One made during the first half of the nineties.