I like the idea of small, roundish objects, like golf balls. They can't be broken, they could be arranged so as to require finesse in picking them up, they're easily availaible, and it could be a real challenge to shuffle them around stragetically. Now, this type of object would create some problems as well, such as field cleanup, making sure there were adequate balls on both sides to make it fair, and the hazard of people occasionally turfing on them.
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