I honestly don't think I could cut it to just three.... In no particular order, my favourites are:
1] Hendrix has to be in there - I'm sure he's a formative one for all of us left-handers especially. Certainly got me to push past the bullshit from every guy who really just wants to sell you a right handed guitar and claim that it's not a 'handed' instrument - or, my favouerite, "You'll havean advantage with your stronger hand on the fretboard" (Yeah? So why don't *you* all play "lefty", then, genius?)
2] Johnny Ramone and Daniel Rey - Ramone for the minimalism, Rey for basically any lead guitar you ever heard on a Ramones album. Also, Rey for that hint of the surf sound on Sheena is a Punk Rocker.
3] Steve Jones and Mick Jones are both guitarv titans in my world. JonesS's crowning glory is that riff on God Save the Queen - a defiant, punk rock answer to the staid, rock and roll establishment best represented by Queen with their take on a song of the same name. Jones M for those wonderful Clash melodies, rooted in old school rockabilly, not least his absolute owning of the definitive rendition of I fought the law.
4] Dick Dale would be an influence on how I listen to guitar even if he weren't left handed, but again being a fellow Southpaw (even if he played it all funny....) helps to inspire.
5] Link Wray. If I can *ever* play close ot sounding like Link Wray, I'll die happy. Primal, true, beautiful.
6] Chuck Berry has to get a mention in there; Johnny B Goode was the song that made me want to learn to play guitar. (Via Back to the Future originally, yeah - except evne back when I never liked it when he drops the melody in favour of all that Van Halen wankery.)
7] Joe Moretti's lead guitar playing on Vince Taylor's Brand New Cadiilac is as near the pure spirit of rock and roll that it's possible to get. (The only track that I think comes as close to fun for me to jive to is JLL's Great Balls of Fire.) If ever there was a single track that summed up everything I find joyful about guitar, it's that one. Moretti was quite the player, worked with a number of big names, but even if this was the only thing he did it still makes him, for me, one of the most important guitar players in history. If an alien civilisation landed and put a ray gun to my head and asked me which should avoid being erased from histroy forever, both from that point on and all memory of it wiped to - BNC or the entire Beatles back catalogue, I'd wave bye bye to Scousers without a second thought. BNC was probably the first true "British" rock and roll recording, certainly it was part of a wider British rock and roll boom that was prematurely killed off by Merseybeat. It hasn't dated the way the Beatles did; BNC Still sounds fresh and alive today.
Beyond those direct influences...
Equipment wise, Lester Polfus. I don't play anything like his stuff (and I am *so* *over* Les Pauls despite many of my heroes playing them), but given his many influences across recording technology, overdubs, being one of the pioneers of the solid body....I'd say he had more influence on pretty much all of us and how we experience guitar music than most folks. Leo Fender would also come in here, but for the fact that he couldn't play a note. And that's not a bad thing - I honestly think that had Leo been a guitar player, he'd never have come up with the engineering marvels he did.
Maybe also Robert Johnson.... I recently worked through his back catalogue again, and somewhere in those 29 songs I can hear a touch of pretty much any guitarist sicne who has ever been worth listening to. Johnson is, I would argue, the ultimate root of guitarp laying as we know it.
Other honourable mentions: John O'Neill (Undertones), Jake Burns (Stiff Little Fingers). Buddy Holly. Bob Dylan is a huge part of why I play acoustic the way I do. THere are lots of more recent players I really like, but these ones mentioned here were my formatives. Really can't dilute it to just three.