Coolest and craziest iPhone 4 cases

Some are funny, some are cunning and some are just downright weird: check out some of the cleverest and most nutso cases we've seen for the iPhone 4.

When someone has a neat idea, others will follow, so you won't be too hard-pressed to find a silicon case that makes your iPhone look like a cassette tape. We're particularly enamoured of the iTape Deck, though; it comes with a cassette case as well, that doubles as a nifty stand for your phone.

If tapes aren't really your thing, keep your eyes out; there are also calculators, game controllers and retro cameras to dress your phone in.

Someone in Japan came up with this, and it's quite spectacular. We can't even say that we don't know what it's for; apparently it's "cute! But sometimes scary!! Naughty Hands off private dock cover iPhone4". Also, as far as we can ascertain, so you can feel like you're holding hands with someone. "A hand full of such love, because it is hand made to take the type of real women and children with eating." Yes, exactly what we were going to say, precisely.

If you're of the crafty persuasion, here's a case you can personalise, either for yourself or as a gift. Mimicking mesh needlepoint fabric, the case is a blank canvas for you to stitch in either a selected design or one you invent yourself. So adorable!

If, on the other hand, your interests turn to construction, this Lego-compatible case allows you to stick little structures or dudes or other decorations all over the back of your case. If you like construction and craft, then you're just going to have to get both.

The Little Black Book iPhone case is really clever. It disguises your phone as a Moleskine notebook, but with a discreet aperture on one end so you can still plug your headphones in.

We're beginning to think there is something about the small, rectangular cuboid that automatically appeals. Certainly we seem to love wrapping up the iPhone thing and pretending it's a different thing, anyway. This leather case is one of the most stylish. It resembles a small book of poetry or aphorisms, but flip it open and you have space for your iPhone as well as credit card pockets and a clear window for easy access to your ID. Just, uh ... don't get pickpocketed.

This one isn't quite available on the market yet, but it certainly looks like it's going to get a lot of love. Designed by Aussies and funded by the brilliant Kickstarter, the Opena is a hardy case with a bottle opener that slots into the back. When the bottle opener is not in use, it slides back in for extra reinforcement. Now that's dual use!

Smartphones tend to have quite low battery life, and the iPhone is no exception. This nifty case adds a battery pack to your iPhone, which has the unfortunate side effect of bulking up the slimline profile of the phone; but some would say it's worth it. According to the specs, you can get an additional two hours of talk time, and an additional 100 hours of standby time.

Cases to turn your humble iPhone camera into an interchangeable lens affair abound, but this one takes the biscuit. Why, you ask? Because of this: "Since the product is made from metal, wireless LAN signals and 3G, GMS, GPS may be difficult to receive." Yes, that is correct. You can add different lenses, but you may end up disabling the phone's ability to function as a, well, a phone.

"Hello? Hello?? I can't hear you, this isn't really an ear! It's a giant novelty ear-shaped iPhone case I bought because there's nothing I love more in a business meeting than holding up fake body parts to my actual body parts! Also, it makes the phone too big to fit in my pocket, so everyone can see it all the time! I'm such a wag."

If you have a spare £5,000,000 floating around, we have the iPhone 4 case for you! The Diamond Rose is a case made out of 18-carat rose gold, with a bezel set with around 500 flawless-cut diamonds totalling 100 carats. A further 53 diamonds make up the Apple logo, and a flawless-cut 7.4-carat pink diamond forms the home button, surrounded by platinum. It comes in a box hewn from a single block of granite ... and yet somehow the effect is of gaudy bling rather than tasteful elegance.

Seen another crazy or brilliant smartphone case doing the rounds? Feel free to tell us about it in the comments below!