We keep thinking something very light that requires accuracy and delicate dexterity, combined with something very heavy that requires force and power.
Some speculate that more accurate driving control may be required.
Feathers? Ping pong balls? Badminton birdies?
Hockey pucks have also been ruminated.
Javelins, ninja stars, crossbow bolts? (From the more aggresively inclined pundits)
...and footballs, of course! .... under water ....
