A rope bracelet - reminds me of making friendship bracelets back in the day. My right second toe used to go numb because I'd hook the end of the bracelet over it, and then knot embroidery floss for HOURS.
This EPIC Bottle Rocket Flew Higher Than our Two Story House! Use a soda bottle, baking soda, and vinegar. Super fun science and backyard project! Demonstrate Newton's law of motion. Also put so glitter in it for a fun explosion