So I have invested in this exact Otterbox Defender Series Hybrid Case & Holster for iPhone 4 & 4S – Retail Packaging – Black from Amazon for $19.89 with FREE Super Saver Shipping.
I’ve dropped my iPhone (with this Otter Box Case) while running before, it bounced, laughed (not really) and kept working with not an issue. I guarantee the results would not have been the same with a flimsy case.
If you love your iPhone like me, invest in the OtterBox Case. Yeah, they don’t look as cool, but it is the cheapest insurance ever.
Pricing was current when the post was published, however Amazon prices change often, so please check before you buy.