There is a great (always busy) sandwich shop in Boston called Darwin's that I used to go to a lot that worked that way. When a customer placed an order they would call down the long line, "anyone else for an X?", then make make the sandwiches with the inner loop over sandwich and the outer loop over ingredient.

I took much delight in the efficiency as well as the incentive structure: If you are not picky and you can help us increase throughput then we'll reduce your latency :)