Black Skylands was a pleasant surprise from IGN's Summer of Games showcase. It's a sandbox sim where you build and customize and airship and use it to explore a vast open world, build skybases, and craft new weapons. It reminds me a bit of games like Terraria, only with a top-down view and at least 200 percent more sky pirates.
The new gameplay trailer provides a nice overview. The idea, it seems, is that you use an airship to discover and explore different floating islands full of nasty monsters and then use an arsenal of guns to blow them up so you can pilfer the island's resources and use them to expand your own sky base. There's even a grappling hook you can use to pull enemies out into the open sky to drop them into the abyss below.