make inuit snow goggels by cutting in half, hollowing out and attaching string and making eye holes
Use as golf balls/marbles/catapult ammo/part of a throwing/ball game
Hollow and carve to make a Mini pumpkin style thing
make a very small crash helmet for a budgie
Glue to the bottom of your shoes to make you taller
Try stringing them together to make a clunky necklace/bracelet/shirt/bra(as a gift?)
Food/bait on a squirrel table (as opposed to bird table)
Use bits of the shell stuck on card to make a picture
See if you can make a pipe end from it
Learn Juggling
These are all theoretical ideas, i haven't tried any, so some
might not be practical
small sugar pot
Fake eye replacement for people with glass eyes
seat or play thing for a small creature
Paint as people and make a family of strange round characters
Yule tree decorations, could be hollowed and filled with something
Grate it to make confetti
Hollow out, fill with wax and a wick, to make extremely cool candles. (This one might be dangerous as they might not stand up and the shell might burn.
Make something like these acorn craft animals
Quite a few things there to keep you busy