splash Masque Clear Screen Protector for iPhone 4 4G  4S AT&T and Verizon (3-Pack + 2 Bonus Back Films)
I use these covers on my iPhone 4 in combination with the[[ASIN:B004AJ718Q OtterBox Commuter Series Cas]].  I have (accidentally of course) dropped my iPhone several times, and even threw it across a room once.  Not a single time has the screen be scratched.  This product is easier to apply than similar covers I have purchased, and lasts well.  Great product.