I see Maria Hill as a Gryffindor. I know a little bit of her comics background, though it's patchy and I ignore bits and pieces of it at will in my WIP about her and Natasha, but she's got the bravery thing down in spades. After all, she was a Marine who got hired by SHIELD by being a BAMF at Madripoor. Not saying all Marines are Gryffindors, just that "Everyone on three!" really fits with her character. The movie showed she's not really all that cunning, which knocks out Slytherin and Ravenclaw for me. Hufflepuff? Maybe, but there are cutscenes in the film where she's not exactly showing great loyalty (I'm grateful those scenes were cut; I like Maria being a bit of a hard-edged woman with some real reservations about the superabilities/reliance upon superheroes, but the movie cutscenes pushed that likability down a little too much).

She is ambitious (in the comics, she runs SHIELD), so she could theoretically be a Slytherin, I guess, but her lack of cunning still rings Gryffindor for me.