Two flash + one continuos

If you wanted to do three point lighting, but only had access to two flash guns and one continuous which light would you use the continuous for.

I see no argument for using it as a back light. Fill light seems sensible because it will probably have the lowest power of the three but I won't imagine power will be a problem for what I'm shooting. Would also stop there being a flash right in front of the person, potentially being more comfortable. I guess though having a continuous key light will make it much easier to see what's happening to the shadows as the people in the shot move.

How would you set it up?