You post a topic, list, category, whatever, in my comments section. (examples: "Five Phrases Batman Will Never Say", or "Five Jobs House Wishes He Had" or "Five Things Dean Will Never, Ever Tell Sam"). Then, in a separate post, I'll post the answers to your Top 5 ideas, according to me. Serious or fun!
Fandoms: Life on Mars, Slings and Arrows, due South, Futurama, Harry Potter, Buffy & Angel, Hornblower, Whose Line Is It Anyway, Kids in the Hall, Spaced/Shaun of the Dead, Black Books, New School Doctor Who and uh... Battlestar Galactica. Does anyone want to take a couple of fandoms off me? They're incredibly expensive but give you endless hours of joy.
Also, feel free to have it be completely non-fannish.