Maybe if you had a free weekend and Mjǫllnir, hammer of Thor, you could crack Corning's Gorilla Glass. But that's a made-up thing! And this stuff is impervious to the very real threats of key scratching and localized pressure.
Gorilla Glass is an unscratchable, unshatterable material used as a protective window for your mobile phone, PMP, or laptop display. It's in 65 products already, and I can assure you that the very nice man from Corning is not faking it. Your intrepid reporter also gave this several tries with all his blogger strength, and couldn't make a dent. I was, however, able to scratch the heck out of some polycarbonate.
Products with Gorilla Glass cost a little extra, but for the bragging rights of knowing your phone's screen is indestructible? Totally worth it.