I like the V-nox opener the best. The trick for me is to rotate the can not the knife. While raising the opener for the next cut I rotate the can slightly(Clockwise). I can usually finish a can faster by reaching in my pocket for my V-nox than I can getting the electric one my wife insists on.
Though the P38 sure is handy, my Chris Reeve Project 1 opens cans readily, top bottom or sides.
Nimrod, I'll second you on that. Fasted way into a can of dog food is lay it on its side and cut it in half. Leaves sharp edges so use a long spoon or tap it out.