I've come to the determination that WidgetLocker is the cheapest, most configurable lock screen.
GO Locker and Magic Locker are both free to install, but each theme can only be configured a little bit. Free ones are rare and limited, and you're asked to pay at every turn. It's really annoying. I scored WL for 99¢ on sale, but even for the full price of $2.99, it's worth it to pay once and never be bothered again.
Also, you can configure your launch screen pretty much any way you like. There are some cool unlock gimmicks I've seen other launchers use, and I wish WL would add some of them, but the fact that you can make your own lock screen is pretty cool. I wish I could configure one up and save it, and repeat, and have a gallery of lock screens I've made, like the others have, but I'm fine just evolving the one as I see fit.
WL doesn't work on its own, and I don't suppose any of them do. You have to download an app called "No Lock" to get rid of the stock lock screen.
And none of these are valid options if you want security. For that, you have to disable your custom lock screen and use the system one.
Samsung Galaxy S3 / US Cellular / d2usc