Zagg Sapphire Defense. Be prepared to be frustrated however as a "perfect" install doesn't exist. LolRelated question: has anyone found a glass screen protector that doesn't have any visible glue along the right and left sides of the screen?
Normally I'd ask specifically about "case friendly" screen protectors. But I've had such bad luck with these things that I'm willing to expand my search a bit.
The Otao protector on Amazon is $10. It's working well for me.