Opena is the world's first iPhone 4/4S case with a slide out bottle opener. This case was first available as a Kickstarter project and I was one of their many backers. If you don't know anything about Kickstarter, you should definitely check it out. It was great to see the guys behind this case with updates on the production side of things all the way to finished product.
As for the review, it works great opening beers. I've used it quite a few times already and it's rock solid. It does add some weight to the phone, quite a bit in fact. That's usually the comment I get from people when I pass my iPhone to them -- jeezus, that thing is heavy.
There is another issue to do the with the headphones. Your standard iPhone earbuds won't have an issue, but if you plug a thicker cable, it will still plug in, but will fall out unless you hold it in. I would suspect the guys to "round out" the issue in the next version. Still, it's the ultimate party case and certainly turns a few heads.