Well Kratos, Nariko, Old Snake, Sepiroth, and the Helghast have been immortalized in a sack suit already. Who else would you want to see "Sack-ized"?
My vote would have to go for Ratchet. I just love that lil' guy :D
Or if Sony and the Gran Turismo guys could work their head around it.. I'd like a Nissan GT-R '07 sack version... (yea i'm an idiot)