A house that combined Ravenclaw's intellectualism, Gryffindor's bravery, Slytherin's Machiavellian ruthlessness and Hufflepuff's...um...something of Hufflepuff's. Their sense of justice/fair play - all those things together would be a lethal combination. Though if you took out Hufflepuff I'm not sure much would be missed.
The courage of Gryffindor, The persistance and hardworking nature of Hufflepuff, the intellegence and beauty of Ravenclaw and the potential and greatness of Slytherin