omg, you dont need a screen protector.
If you are not the kind of person that throws stuff around like my retarded brother, and also not the kind of person who is careless and drops stuff and dosent think anything of it, then you are set. The only way you can scratch the screen is by taking a knife, applying a good amount of pressure, and just digging in to the screen. There you have a scratch, otherwise, you will probably crack your screen before putting a scratch in it. It is made out of treated glass which resists all normal wear and tear.
But if you think I am stupid and dont know what I am talking about, then I recommend Zagg InvisibleSheilds. I had full body invisibleshields for my iPod Touch 1st gen, and never got any scratches on the whole iPod or even the invisibleshelds. They are made out of a kinda rubbery material which is great at resisting scratches. If you run a knife over them, it will just leave an indentation which goes away in a minute or two. The only reason I got them was to protect the chrome back from getting any scratches, and they worked great for that.
You can choose weather you want full body or just a screen protector like what you want. Watch some videos about them on youtube.
Zagg InvisibleSheild