I purchased one of those inexpensive "Silicone Rubber Skin" cases from eBay for $4.00. It works fine and it will be impossible for you to have it slip out of your hand, nor will it slide off a surface like a dashboard.
It doesn't fit as tightly as I would ultimately like, in part I think because the screen is so big and goes almost side to side and top to bottom on the phone... Not a lot of room to have a lip that grabs. Still, if it were only manufactured to be slightly undersized, it would be a better fit.
You could get one of these as you search for the ultimate skin/case.