Circular Knitting Needles
Knitting isn't just knits and purls; it's also needles. While you can start knitting with regular knitting needles, as you get into the hobby you'll soon find that many projects -- particularly circular ones like socks or sweaters -- can require several different sizes of needles.
Instead of buying a separate needle whenever you need a new size, you can get an interchangeable circular needle set that comes with cables and several different attachable tips. Kits can vary widely in price, but for a splurge-worthy set, consider spending $150 to $200.