^ I don't really see how Hecate is overused. I doubt her screentime amounts to even 10 minutes through the whole season. She barely had any appearances aside from her attack on Yuji to seal silver again and the very last episode.
If i were to say which character is overused, it has got to be Kazumi. She didn't really have a purpose and the writers didn't really seem to know what she is supposed to do either. Her involvement in the story lacks any form of creativity and she is very limited in her actions, which would amount to thinking one thought: "i want to stand in the same place as Sakai-kun and Shana-chan".
Her role in season 1 was much more defined and her presence more meaningful. But it seems that after fulfilling her role as Shana's rival in season 1, now it seems the writers simply had ran out of ideas what to do with her, thus she ends up as presence with barely any purpose.
As for my favorites ... i am not really sure i have one
Yes, i have some characters i would prefer over others, but i don't really like any of them to the extent i would want to vote for them on the poll and say "yes, this is a charater i like from SnS".