For powers of 2 I like multiple coins and binary, but it turns out the average person doesn't understand that, even with an explanation, and is likely to think you're making it up as you go. As I found out when I did a 'raffle' on a tatting mailing list once, and got 64 replies. I told them I'd pulled out 8 pennies and used binary and it was a big huge "whaaa?"