One of the best perks about working for Gap when I was in college was I was able to buy Gift Cards at 30% off. Well, I don't work at the Gap anymore, but they are offering a great deal for Old Navy Shoppers! Between now and December 24th, buy Old Navy GiftCards and get 20% off. Talk about a deal!
The great thing here, I believe that you can still use Gap Inc. Gift Cards anywhere - so you can shop at Banana Republic AND Gap. It doesn't look like you will need a coupon, just check with your cashier to see if their store is participating.