If you're a knitter, you need yarn. I don't knit, but I find yarn stores (and notions shops, quilter's stores, other crafty places) absolutely irresistable. If I find a beautiful store overflowing with innumerable shades and textures of charming little yarn balls, I'm sucked in. I have three pairs of needles and a few different colors of yarn...all bought at the Yarn Barn, because when you walk in there, you want nothing more than to become a knitter.
They're also surprisingly sweet and tolerant of someone with my affliction - if you are someone who actually does need yarn, I can't recommend a nicer shop.