Sorry it's taken me until now to reply, I haven't been very active lately.
My favorite character from SAO would have to be Asuna, but I'm still working on season two, so who knows? Maybe I'll find another favorite character. MY favorite part was probably all of the first half of season one, because it captivated me so much. When they brought in the fairies I was still somewhat captivated, but not as much as before.
What about you?