Soujirou - Even if he refers himself as a 'failure', never ever underestimate how great he is!
He raised Konata mostly by himself alone, is a skilled writer who can make enough money to live happily, is as knowledgeable as Miyuki at the very least, and is a good-hearted, modest, and really strong and truthful person, with a little bit of twist.
Konata - The divine yet cursed avatar of all that otaku!
Kuroi-sensei - A great teacher, or, more than that, an excellent person.
It seems she's too good to have her own happiness, though...
Miyuki - She's cute, attracting, thoughtful, kind, and 'useful'. She is all what others think of her. And thus, she's the one who is never really understood. Sad thing, but this is so real.
If Konata or someone else could steal her lines, she would have looked more interesting...
Kagami - The ideal tsundere and even more than that. I don't like 'tsundere' characters basically, but I think I can tell how she developed her personality...
Also I think her name really fits her character.
Hiyori - Utter otaku without a partner like Kagami but her own better self.
I sometimes feel sorry for her but it's so hilarious.
Ayano - Misao's 'better half'. I also believe she is very unique and interesting,
yet the sole mysterious person in the series.
And I didn't check Minoru: I think he's a bit overrated.
Not that I hate him, but Lucky Star is not supposed to be his story!