Target has a sale on Sally Hansen nail polish where you can get one free when you buy 3. There are coupons to match up with this sale too.
Sally Hansen Nail Polish $2.59 ~ Buy 4
Get one FREE when you buy 3 (-$2.59)
(3) $1/1 coupon from 7/28 Red Plum insert
Final Price = $1.19 each
Most Target stores will not allow a coupon on a FREE item, but if yours does your final cost will be $.94 each.
Make sure to check the clearance too, there are lots of Sally Hansen nail polish on clearance you may even be able to pick some up for FREE.