Murray easily has the best backhand lob in the game. Up there with Hewitt among the best I'd ever seen. Nalbandian's backhand lob was great when he had time, but not necessarily from defensive positions.
If we're talking about defensive lobs (ie not winners, but lobs just to get back in rallies), then it's Djokovic and Murray. Nadal and Federer used to be up there too.