I've missed a couple of questions and was happy to see these two easier questions:
1) What yarn (that you don’t have/haven’t used) would make your stash “complete”? I have never tried cashmere yarn and think it would be neat to have a little sample.
2) What yarn do you never want to be without? I'm really loving the Malabrigo worsted and lace weight yarns. I also love Dream in Color Smooshy and Classy. Don't really need any of the Smooshy until they release some new colors, though.