Sherlock Holmes; Ravenclaw I debated Slytherin for him, since he has the cleverness, wit, intelligence, and the drive for personal gain, but at the end of the day, Sherlock’s world revolves around the pursuit of knowledge. His need to show off his prowess is secondary.
John Watson; Hufflepuff John is, to me, as Hufflepuff as one can get. His bravery and loyalty are defining qualities for his character. Seemingly small and harmless at first, when his loyalty for Sherlock is put to the test, John would drop everything in an instant to protect not only Sherlock, but also his reputation and his heart.