I think these clip-on SNARK TUNERS are a great value...

in addition to costing less than the average guitar tuner (which only recognizes the notes EBGDAE) this tuner recognizes all notes, which makes it useful with other instruments that aren't tuned like a guitar.

Or, if you want to tune your guitar down a half step to Eb Bb Gb Db Ab Eb, this tuner can do it, whereas a conventional tuner would choke.

And the fact that you don't have to plug unto it makes it perfect for acoustic instruments