I have a friend who's a Hufflepuff and she's one of the nicest people I've ever met! I'm a Hufflepuff too, so thanks for talking us up!
Half Blood Prince and Deathly Hallows.
I wouldn't bring back anyone. As much as the death of characters destroyed me, they shaped Harry into what he is now. (But if nothing changed, then Fred, because I can only imagine what his death did to his family. Then Lupin and Tonks since they have a son and deserve to raise him and be there for him).