Minerva McGonagall, head of Gryffindor, deputy headmistress, and after Dumbledore's death and after Snape leaves, acting headmistress.
She's a stern lady, but she does have a caring side. I feel if she would be someone you'd want to be locked in a cave with. What I mean is she'd be really caring and motherly, but also really strict, and help get you out.
I love the scene in Deathly Hallows when Harry appears out of his cloak in the Ravenclaw Common Room almost giving McGonagall a heart attack. I wish that had been in the movie.