My nickname is still giving you trouble, Mare?
As far as answering the question, no, I don't think people can guess who's my favorite. That is, unless you have read "Memories" (please don't, it sucks big time, I just don't have the heart to delete the thing).
Most of my stories have Nick as the main character. I think that is because he's just easy to torture
When I started writing, I often chose him, because to most people he is/was the cutest/hottest, so I got more reviews (which helped me improve my writing). Nowadays, I choose him, because to me, he's still the most complex, naive, clumsy one AND the one without the whole complication called "a family". Although I could leave the wives and kids out, for some strange reason it doesn't seem fair. Did I mention I am a bit crazy sometimes?
Since Nick is somewhat my least favorite (although I usually don't categorize them as such anymore), I hope I am doing a nice job at hiding that fact.
Edit; I forgot to answer one of your questions!
Back in the day when it was really important to have a favorite, people were always surprised to find out that for me, it was and still is Kevin. Nowadays, I rarely discuss my fandom with people who aren't fans themselves. My colleagues were surprised though, seeing as my ex-boyfriend looked a lot more like Nick LOL.