Verify Varieties: Most sale items are only valid on certain sizes and flavors/varieties, so you can double check your store ad for specifics. And if you can't find the correct product, it helps to have the ad when asking an employee for the product location.
Store Coupons: Not sure which store coupons you'll be using or don't have time to clip all? Bringing the ad with you and clipping just the applicable ones can be a time-saver.
Price Verification: Store ads are great for double checking prices both in the aisles and at the register. This is especially nice on the first or last day of the sale when sale prices might not all be in the system.
Rainy Day: If a product is out of stock, have the store ad with you to show the cashier so they can write you a rain check for the correct product, including size restrictions, included varieties, and limits.
Time Shortage: If your schedule is tight, store ads can still help. Grab a copy at the entrance to see what the best prices are on items like produce, meat, bread, and dairy.
Price Matching: When matching ad prices at supercenters like Target and Walmart, it helps to have the applicable competitor ads with you. Note that the Target policy requires the ad, while the Walmart policy states that you do not have to have the ad with you (but you'll find it helps to have it just in case!)