What is your favourite spell?
Avada Kedavra, obviously.
No,I'm just kidding. Well, I love many of them. From the sound I would have to say Wingardium Leviosa, Muffliato would be so helpful, but I think I have to go with Expelliarmus here because I so impressed by Harry only ever using this spell and not even considering to use one of the more lethal spells. Harry manages to get through all his life of Voldemort chasing him and fighting him without ever touching the A-spell and for that I can only draw my hat.