ChordMaster

$1.99 (iTunes link)

ChordMaster does just one thing, but does it very well: demonstrates where to place your fingers for any guitar chord.

Pros: Intuitive interface, tons of chord parameters (major, minor, diminished, dominant) great graphics, authentic sounds and strumming. Info screen includes options for left-handed orientation.

Cons: Not all-encompassing like Guitar Toolkit. No options for alternate tunings. No full-screen fretboard view. No suggestions for chord progressions.