Knights vs. Aliens is a brand new title to the App Store that serves as an interesting update to one of my early App Store favorites, Galcon. Instead of sending triangles around between planets, though, you're pointing squads of knights around the world, trying to take over castles from aliens, of all things. There are a few updates to the gameplay, mostly in the 30 various maps that offer strange combinations of routes and castles to fight through.
There's also a fun sense of humor throughout, and that always makes for a good time. There's no Game Center or OpenFeint integration, and there's no multiplayer either, so those will have to wait for any updates. The game is out right now in a universal version for US$2.99, and if you're a big Galcon fan, it's definitely worth checking out. If you've never played this kind of game, Galcon does have a lite version, and the great Galcon Labs (featuring a few other twists on the standard gameplay) is only 99 cents. I'd love to see some even deeper strategy games on the App Store; if you know of any more solid strategy titles (real-time or turn-based), feel free to share in the comments.