Terraria, the breakout PC and Xbox 360 game from Andrew Spinks, is a 2D side-scrolling retro-pixel game that takes a ton of inspiration from Minecraft, with a fan following almost as big.
If you've played the console or PC version, you'll recognize the iOS version immediately. It will be a universal app, and the dev team wants to add Game Center and iCloud support to allow you to play across the devices seamlessly. They also hope to add local Wi-Fi multiplayer support in a post-launch update.
Here's a quick video to spark your interest.