BaseOneLabs's ($25) is, according to the company, "quite possibly the toughest bumper case available for the iPhone 4." The super-dense, shock-absorbent case features a 360-degree raised lip around the front and back to protect your iPhone from face-down and face-up falls. If you want proof of this case's abilities, check out the company's Website for a video of a guy dropping his Impactband-encased iPhone off a pretty high ledge onto the concrete below.
($35) is, like the rest of the company's cases, made of biodegradable and environmentally friendly materials--the "bioplastic" is based on plant material. Along with providing impact and scratch protection for your phone, the Bioserie case also boasts a specially designed opening for the phone's flash that claims to prevent hues and unwanted coloring during flash photography.
Despite it's rather depressing name, Bluetrek's series of cases ($27 each) sport some rather uplifting graphics. The 1mm-thin, hardshell cases are built from lightweight, "2H Scratch-resistant," recyclable plastic and feature artwork by French artist Aurele, who's responsible for The LostDog's namesake.