a Fanboy seems originally a term applied to anyone into comic books, sci-fi, or other 'odd' hobbies. Now fanboy is typically reserved for over the top fans of comic books that dress as their favorite heros, and star wars fans, who seem to do the same.
I wasn't about to wait in line for five hours to see the new star wars film, not with all those fanboys standing there in their stormtropper costumes!
A noun, trekkers are originally fans of the TV show Star Trek: the Next Generation, and used the term 'trekker' to differentiate themselves from the original star trek fans who called themselves 'trekkies' Trekker has now come to mean a Trekkie who doesn't understand that they're a trekkie. Within the star trek community, there is still a debate over the difference between trekkies and trekkers, but the only difference is that trekkies came first, and trekkers don't like the term 'trekkie'.
"I came up with the term trekkie. So, it's trekkie, not trekker."
Gene Roddenberry, Star Trek Creator.