I would go with six pound P - Line Fluorocarbon LEADER MATERIAL. It is tough as nails and has great knot strength. Just not suitable for main line of course. Have landed the pike on the 12 pound and had only one bite off in five fish hooked in two trips. Still for pike I would go heavier, but for walleyes, since they don't have the jaw pressure pike have or as many teeth, especially the ones on the roof of mouth, six pound is fine. Never have had a walleye bite off in hundreds caught.
Tyler