This Perricone MD Vitamin C Ester Brightening Serum ($69) boosts your skin's radiance with a vitamin C compound that also includes antioxidant ferulic acid. It's earned a 4.5-star rating with more than 10,000 loves from other Sephora shoppers. (For stubborn dark spots or more severe discoloration, the serum works even better when this product is used during the day and alternated with the Vitamin C Ester 15% Intensive Brightening Regimen at night.)