Probably the late Leonard Cohen.
There are several that I would rate as a 10 out of 10 but the questions was ONE.
However I will still state some of my other favourites!! Sandra Bullock, Cher, but my all time favourite celebrity would have to be Leonard Cohen who I saw several times when he was in Perth, and who had the best concert ever....
Im sure as people answer, there will be others that could come in at no. 2 etc...