Two boxes of Cheerios for price of a gallon of milk
Buy two boxes of Cheerios, which are on sale 2 for $4. Use two $1 off 1 coupons to bring the cost down to $2.
Buy a gallon of milk at the same time and you'll get $2 in Register Rewards, which are like cash vouchers you can use toward a future purchase.
You'll get two boxes of cereal, plus $2 in Register Rewards, plus a gallon of milk for the cost of the milk. Not too shabby.