For me it's my SAKs hands down. I don't think I've ever had trouble sharpening them....sandpaper, stones, pebbles, rods, cement...could write a long list of things I've used on em. I think with how tiny the blades are, that helps me to get em sharp quite a bit. With higher end steels like S30V my sharpening skills are laughable at best. 
What's yours?
What's yours?