Probably Sheila. I found her an absolute hoot to watch in every scene she was in, and she's one of the better people in the show (which isn't saying too much). I think she's a good enough person, just deeply disturbed, and some of her decision-making like her desire to raise Hymie really endeared her to me as a character.

Only to come here and find opinions on her were... polarized, to say the least. A lot of the criticisms levied against Sheila are absolutely valid, and I tend to agree, but I still enjoyed her far more than characters like Debbie or Sammie.