Frank Zappa wore many different hats during his mind-bogglingly prolific career. On any given recording, one is just as likely to hear him as the mad avant garde composer, the big band front man, or the quirky, potty-mouthed master of ceremonies. Of all his personas, none have had the impact nor the influence than his identity as guitar god.
Droves of fantastic guitarists with myriad signature styles have listed Frank Zappa as an influence, and it really is no surprise. Not a single musician can write and play as many different genres with as much mastery as Zappa did, so any guitarist can find areas of Zappa's playing to glean inspiration from.
Traditional "rock" tonalities and time signatures were largely thrown to the wind in his compositions and improvisations, which helped to further define the uniqueness of his approach to the instrument. No guitarist, no matter how individual their sound, can be as easily recognized as Zappa.
Whether using the whole-tone scale to stretch the limits of harmonic possibilities, or insisting on improvisational sections of his concerts that no one (himself included) knew the destination of, Zappa challenges listeners to eschew passive listening in favor of active evaluation and challenges everyone who touches a guitar to be as inventive and virtuosic as possible.
Here's a few samples from his massive catalog of the power of his playing. This is only the tip of a very large, very impressive, very rewarding iceberg.
Shut Up 'N Play Yer Guitar