Great thread general Hercules.
Federer's single handed backhand is underrated by many because of the criticism he takes from it breaking down under the power of Rafa's topspin.
But it seriously has to be considered as one of, if not the best. I believe his variety off that wing with quality along with his uncanny half volley and wrist flick ability is second to none.
Wawrinka gets my vote for most power with consistent accuracy.
The others mentioned are also very, very good.