Challenger One: Furukawa Nagisa
A sweet girl that has been away from school for a year, and wants to start up the drama club again. She was the main heroine of the CLANNAD game and movie. And she seems to like wearing cute nekomimi!
Points for: It's like last year's debate with Ayu and Nayuki; the latter might be on some covers, but the former is the undisputed heroine. Queen of the merchandise, biggest part of the OP for herself, the story that makes you cry the most. This would be no contest, except...
Challenger Two: Sakagami Tomoyo
There's her. A new transfer student with rumours all around her, she's tough, disrespectful and can beat any classmate up. She's also got a talent for cooking... someone please think of a tough-girl renai game character without a secret domestic talent?
Points for: Well, there's one. She had her very own H-game sequel. Everyone's been going around saying that the Toei-Kyoani duo (or just the latter, actually) has to animate every Key game (never mind that One: kagayaki kisetsu e already had its own OVA, didn't it?). How can they do so if Tomoyo doesn't win? If she does win, I bet either Tomoyo After will get its own anime, or it'll be referenced in an epilogue.
So... who do you think it'll be? Personally, I dunno. I just wanted to have some fun. (My bet's on Nagisa, but if I say it, Tomoyo might attack me...)