I got this silicon sleeve protector after trying a hard-shell case and not liking it because of the extra bulk.  This sleeve doesn't provide much protection from drops, but it does provide a better grip on the phone, and protects the back from scratches when you set it down.  It will also provide a little more clearance between the screen and a flat surface if you set it down on the front.  It also adds almost no weight or bulk to a phone that is already quite large.