If you've got any musical interest at all or simply like impressing college girls, you should definitely check out ChordPlay. This app has basically created a virtual guitar preprogrammed with all the chords that you could possibly think of. If you can think of more, well it will even let you add them yourself.
There are two ways to use ChordPlay: Play and Chords. In Play, you can set 12 favorite buttons to instantly load any chords you like, then strum away at the bottom of the screen. You're capable of just strumming a specific string if you like, making the 12 favorite limit seem even smaller.
In Chords, you can just play through all of the chords either one string at a time or as a solid chord. You can also edit or create a chord at will by pressing the appropriate button. While you may not necessarily be making a real chord, you could make a series of individual strings you need on one set to play a full song in Play mode.
If you've got no musical experience, you may get bored with this app. However, it seems like anyone with even a bit of guitar knowledge or the desire to learn some more about guitar would actually be able to play a full song out on this app. For a music app, this is one of the best ones out there so far.