Another week has gone by, which means that it's time for another one of our trademark iPhone-case roundups. This installment features the usual mix of types (and, as it turns out, shapes), and it illustrates the fact that the market is so huge that manufacturers don't hesitate to experiment with new materials, unusual features, and odd add-ons.

(Image Caption: CM4's Q Card)

CM4: The Q Card (iPhone 4 and 4S; $40) is a case-cum-wallet made of faux leather that, according to the manufacturer, can comfortably hold three credit/debit or ID cards and some cash, eliminating the need for carrying a separate wallet. The case also includes a protective cover that keeps your iPhone's screen free of scratches and skin oils.

(Image Caption: Holga's iPhone Lens Filter Kit)

Holga: The iPhone Lens Filter Kit (iPhone 4 and 4S; $25) is…well, rather unique. As a snap-on case, it protects your handset from dust and scratches while providing a comfortable grip, and it's available in black, white, silver, red, or blue. As a lens kit, it comes with a sort of color wheel that provides you with eight special lenses for enhancing your photos, with effects that range from artful distortion to colorization.

(Image Caption: InCases's Snap Case Warhol Collection)

InCase: The Snap Case Warhol Collection (iPhone 4 and 4S; $40), which we covered back in a September roundup has just been extended with six new designs, including Andy Warhol's famous self-portrait. Like all the company's Snap Case models, the cases in this collection provide snap-on protection that's both sturdy and resistant to scratches and dents.

(Image Caption: The Opena)

Opena: The Opena (iPhone 4 and 4S; $40 AUD) combines a sturdy iPhone case with an equally sturdy stainless-steel bottle opener—perfect for when you're out and about with your phone and a screw-top cap is nowhere to be found. The case, made of PC/ABS plastic, is available in black or white.

(Image Caption: One of Pong's iPhone Cases)

Pong: This company's iPhone cases (iPhone 3G, 3G, 4 and 4s; $40 to $60) promise protection from the radio-frequency radiation emitted by cell phones. According to the manufacturer, each case can reduce radiation leakage by up to 95 percent below FCC limits without compromising a handset's reception. Four different models are available in a variety of materials and colors.

(Image Caption: USBFever's Camera Style Case)

USBFever: The Camera Style Case (iPhone 4 and 4s; $17) is designed to make taking pictures with your iPhone easier than ever. Its contoured grip helps you hold your handset firmly in one hand, while a shutter-release button works nicely with iOS 5's volume-button shutter functionality. The case even comes with a handy strap that makes it easy to keep your phone at the ready.