Aw, what’s wrong, Phase42, did I put a damper on your mood? 
Okay, okay, I’ll shut up now.
I’m surprised nobody’s mentioned the (IMNSHO) best guitarist of at least the second half of the 20th century: the late Michael Hedges.
That man reinvented the guitar. I would die a happy man if I ever learned to play “Aerial Boundaries”. When asked what his style was, his favorite response was “Violent Acoustic Guitar”. And he put on a hell of a show live. I was lucky enough to see him in concert twice. I wanted to go home and hide my guitar in the closet after each show.
But Jimi’s ear was so good he could re-tune while playing.
Jimi was a lefty playing a right-handed guitar, but it was strung ‘normally’ (low E on top). The knobs and switches were on top that way, and I always wondered if that was more convenient than the usual layout.
There are some other guys who did play genuinely upside-down guitars.
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This guy continues to floor me. I can play as fast as D.G. It’s not that tough. One thing the guy’s got in spades (and I’d also put Jeff Beck in this catagory…Gilmour sounds like Beck without the speed sometimes) is immaculate vibrato and pitch-bends. So many upstarts simply beat the shit out of vibrato, either making themselves sound like epileptics on crank, or blowing it so wide open you could drive a truck through it. It’s very hard to replicate D.G. vibrato, and even harder to get the pitch-bends to glide into place with his degree of perfection.
Anyone with left-hand technique comparable to D.G.'s who can ramp up the tempo and throw a little right-hand magic in is a true guitar diety, in my mind. Beck fits the bill nicely.
Agreed - Beck is the best to my ears, but Gilmour is mighty tasteful. My story - Gilmour works out his solos completely - often before they are matched to a song. A friend who is a record producer was working with him and when David heard a chord progression, he stopped the players and said “wait, I think I have a solo that fits nicely there” and trotted it out.
He is a truly, truly great player, but I give Beck major points for his ability to be more aggressive when called for and for his deep improv skills…
It would be pretty fun to see those to in a…I dunno, portomento duel of some sort. Beck would win, of course, but still…
No, I’m just always on the lookout for opportunities to provide a good spanking 
I knew that, but it does mean the bridge pickup was angled the “wrong” way, the whammy bar was in a strange position and the headstock being the wrong way round might’ve altered the string tensions (maybe). I think he would’ve sounded exactly the same on a lefty but playing an upsidedown guitar was definitely a style choice.
Yup, one of the Alberts IIRC, and there’s a guy in Roger Water’s touring band who plays a left handed guitar strung right handed, that is weird to watch.
What I’ve read in interviews is that he uses all sorts of approaches, at the end of Childhood’s End off Obscured by Clouds you can hear him singing along with the guitar. Probably most of his solos are semi improvised.
Clothahump Michael Hedges is (was :() scary. I’ll chuck in in Leo Kottke – another guy who plays guitars with too many strings in strange tunings. If you hear a bottle-neck on a 12 string playing something impossible it’ll be him.
While I’m here another distinctive, non-virtuoso occurs to me, Neil Young. I bet all the guitarists here could recognise his sound from a single note.
There’s a stroy that Jon Bon Jovi once told about how he hired Jeff Back to play a solo on one of his songs - “Balze of Glory” IIRC and Bon Jovi was very excitied about seeing how Beck got his sound etc. Bon Jovi asked did Beck have any special reuirments for the session, to which Beck replied “No, just rent me a Marshal” “A Marshal?” asks JBJ “Yeah, any Marshal” says Beck. And sure enough, he just turns up with a Stratocaster, plugs in and plays. Bon Jovi figured the sound just came straight out of his fingers.
Same thing with Neil Young when he amps up with the Horse - thats the sound that just seems to flow out year after year.
Angus Young from AC/DC you can tell by his vibrato (tremelo/ululato - never sure on the exact difference) and that guys hand’s are TINY - but he has such power and precision, you can pick him.
To me, Hendrix’s fluidity and that sheer sense of joy in his musc are what set his sound apart. I cannot define it, but to my ears even in his heaviest blues, you can tell that guy really loves playin’ on his git-aur.
Peter Green - another guy whose tone you could just tell a mile away. Frank Zappa always had a nasty, nasty sound, too. It’s their voice.
mm
As you can tell from other posters’ input, guitar sound is as distinctive as voice or fingerprints. Sure, a lot of it is effects, amps, etc., just like a lot of sexy womens’ allure is clothes, makeup, hair, etc., but the way someone moves/speaks is as telling as DNA, and this extends to guitar playing.