The best thing about Guitar Tuner Free - GuitarTuna is not only that it offers exceptional features, but also that it has a really easy-to-use interface. Accessing each feature is really simple. You can also use the integrated metronome with just a tap on the screen. Likewise, there's an entire chords library where you can find lots of different diagrams.
Guitar Tuner Free - GuitarTuna is one of the best tuning apps for Android if you need to tune a string instrument. It includes a lot of other features as well, like the metronome and tab library.
Requires Android 2.3 or higher