Crayola Ultra Clean fine-tip markers (come out with water and a bit of laundry detergent) and Crayola Ultra Clean fat-tip crayons (come out with spritz of water)
I also love those little sticks Joanne & HL sell in their cake decorating section (to make cookie bouquets). They are great for puffing out yo-yos & I recently used one together with the top of a prescription bottle to make a spindle to hold my extra bobbins. They are exactly the perfect size to slide the bobbins on.
I have also used them as individual spindles for storing my thread on a CD case.
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I also used empty Whitman's chocolate boxes for a sewing machine surround (since don't have a sink-in table yet). Such a hardship to eat all those chocolates so I could do my quilting.
And, of course, the basics: masking tape, freezer paper, tweezers, pens/pencils for pattern making & such; plus, I always keep a Sharpie handy for labeling dates on my Aurifil thread. I store small notions for my hand work in cosmetic bags.