Guitar Tuna is the most used application to tune stringed instruments, from guitars (acoustic or electric) to bass, banjos, mandolins, ukuleles, and many more. This program is very visual and simple to use. It includes a metronome, a chromatic tuner, and games to practice chords or learn songs, among other options. It also allows you to store the different chord diagrams in your library.
Guitar Tuna works with your device's microphone, so it does not require cables, and incorporates a background sound cancellation function so you can use it even in noisy environments. It's suitable for both beginner and professional musicians and is completely free.