GuitarTools is a multi-platform application for guitar and bass players of any style. It can also be used by other fretted instruments players, as you can customize the number of strings, from 3 to 10, the strings and neck appearances, and the tunings to use.
It's a learning tool which helps you finding scales, chords, voicing, harmony, and practicing. It comes with a bunch of useful features and customization: right- or left-handed neck, different guitar and bass sounds, metronome, favorites tunes, circle of fifths, diatonic chords and scales, printing and copying the neck, and more. The neck can be customized to suit your own guitar: wood, inlays, inlays shapes, frets, strings shapes, etc. More, you can use several necks and quickly change from one to another. You can open several windows, for example, one showing a chord and another showing the relative scale. The favorites tunes "Player" can play almost any video or sound files. See the screenshots and manual for more details. Guitar Tools is available for Mac and Windows, and is localized in English and French at the moment.