Developer: Bonnet Inc.
Price: $0.99 Download on the App Store
I've seen a lot of great iPhone applictions, but it's been a while since I've seen one as clever and entertaining as PocketGuitar. PocketGuitar turns your iPhone into a virtual guitar, allowing you to strum and press strings as you would on a real guitar. Whether or not you're a guitar player, it's a blast strumming the virtual strings and trying to coax a chord out of your iPhone.
The app comes with six built-in instruments (Acoustic/Electric Guitar, Electric Guitar, Classical Guitar, Muted Guitar, Electric Bass, and Ukulele) and an extensive library of effects and tuning options. PocketGuitar uses the iPhone's accelerometer to great effect; when you shake the phone it wobbles the pitch. There's even a setting for lefties to switch the app into left-handed mode.
Just like with a real guitar, any non-guitar player will have a hard time making the thing sound halfway decent. That said, PocketGuitar is a lot of fun to play around with and gets an immediate "wow" reaction out of anyone seeing it for the first time.