A Fandom is essentially an empire full of supportive fanatics for any particular franchise. The fans are actually the ones that name themselves. Not the franchises.
Are you fighting with a friend because they are Team Edward (or Team Jasper could be another possibility) while someone else is a Team Jacob (or other possible pack member)? Twihards for those who are obsessed with anything to do with Twilight, in which the aforementioned teams are a common indication of obsession. I will admit that I am a Twihard.
A Whovian if they prefer to follow Dr. Who. So, essentially you will be talking about one of the many doctors. Or, perhaps you wish to talk about the TARDIS?
Or, perhaps you are an Otaku? Which, means that you are essentially addicted to everything and anything in relation to the Japanese, Chinese, or Korean franchise? Again, I would say that I am a Japanese Otaku, considering that I prefer to keep up with animes, mangas, or even writing fan fictions.
AFA-08 (Photo credit: Hitoribocchi)
(Image is that of someone cosplaying as Renge Houshakuji, a character from the anime/manga series of Ouran High School Host Club. Renge is an example of an Otaku.)
No matter what you choose for your fandom(s), feel free to go wild!