I've nearly talked myself into Kathy's being the Sabo.--she wasn't on the couch in the before shot (if that was really the before, shot, I do wonder about that)
--she's on the couch at one end...and she's the first to get up and harass Andrew for scaring them
--she covers her mouth when the Sabo is talking...isn't that one of the tells on "Lie To Me"?
--she covers her face with a pillow saying "nooo" or something like that when the Sabo tells there is slop available. (Maybe to suppress a laugh?)
--she sucked in the HOH challenge yet looks to be a fit deputy.
--I also think it's hard for a 40 year old woman to win BB when there aren't many of her peer group in the house. Deciding to play for the $50k fits.
Several of the house guests have sh!t eating grins though,--Matt, as someone mentioned above, is one. Brendan and Andrew.
I'm ruling out Enzo, Britney, Hayden, and Rachael.
My second choice for Sabo is Monet. She was on the floor after the lights came back on, was missing, and probably assessed that winning $10k would hurt her later in the game and not earlier in the game so she went for the prize.
Her body language is part of what makes me think of her as the Sabo.