Professional sewing (I mean, being able to make anything that you need a sewing machine for: stuffed animals, clothes, blankets, etc.).
Just FYI I actually do most of my sewing by hand, without a machine.
Hand and machine sewing both have their strengths and weaknesses, but for most things I much prefer doing it by hand.
I would like to learn to knit or crochet someday, which I probably will, but I dunno when, I have no free time! I also want to go back to weaving, but I'd have to get a loom and they are expensive and take up a ton of space.
Metalworking, glassworking, leatherworking, those all interest me too. Really I'm interested in most arts, crafts, and hand-making skills. But there are so many to learn and only so many hours in the day!