I suppose I'll start
Bob Dylan:
When most people think of Dylan's work they instantly think of his protests songs of the early 1960's which to me is a shame, when post-electric era Bob Dylan has so much to offer. While Bob Dyan essentially spent the majority of his career playing rhythm guitar, one only has to look at examples of him playing leads such as 'Leopard Skin Pill-box Hat' to diminish any thoughts of inability. One of my favorite aspects of Dylan's playing and compositions are his ability to take traditional blue sand folk chord progressions and put a unique spin on them, producing results that still fail to sound dated to this very day, although in most cases the works are 30 - 40 years old in reality.
Neil Young:
While many may think of the laid back country-folk stylings of 'Harvest' when thinking of Young, it is perhaps the polar opposite in his work that proved to be most influential, as one can not deny the sounds of his work with Crazy Horse had a profound impact on both hard rock and grunge in the early to mid 90's. In my opinion the best demonstration of this occurs in the album 'Everybody Knows This is Nowhere' where Young's soaring leads are a stand out feature contrasting against the jam based playing of Crazy Horse. Neil Young's composition and singing skills only serve to strengthen the impressions of his guitar playing while many artists playing would only suffer from such skills.
Robbie Robertson (The Band / The Hawks):
Perhaps one of the most interesting guitarists of the past 50 years, Robertson's main appeal is the blend of American pre-rock n' roll styles (including bluegrass, folk and jazz) which is apparent in his compositions, in a time where rock n' roll was dominating the writing styles of his contemporaries and even co-collaborators (such as Bob Dylan), in fact Robertson was infamous for his lack of use of staple rock n' roll chord progressions. His body of work shows an amazing versatility from the almost funk driven sounds of 'Up on Cripple Creek', to 'Rag Mama, Rag' which echoes mental images of the Southern United States, to the mystical jazz styling of 'Somewhere Down that Crazy River'.
Lou Reed (Velvet Underground):
Often described as 'The Godfather of Punk' Reed's early compositions only reinforce this title, particularly those with the Velvet Underground. These works typically only contained two or three chords and would succeed in creating a droning effect in the music creating an essential part of The Velvet Underground's sound. My favorite of Reed's guitar playing occurs on the Velvet Underground album 'White Light / White Heat' where both he and Sterling Morrison experimented with high amounts of gain and audio feedback creating a work which still sounds daring to the present day. Of course let us not fail to mention that we have Mr Reed to thank for bringing the smut to rock n' roll with songs dealing with issues such as drug dependency, prostitution and trans-gendered individuals.
Nick Drake:
To me Nick Drake's most interesting quality as a guitar player is his uniqueness, I have come across very few guitarists who could even be compared to Drake with his virtuoso finger picking techniques, use of cluster chords and experimentation with time signatures in an extremely conservative genre. Drake's compositions although primarily folk combined elements of jazz, various forms of world music and laments of pop, showing sensibilities which afforded him opportunities to work with some of his finest contemporaries including the Fairport Convention and John Cale, despite his lack of commercial success during his own life time.
Johnny Thunders (The New York Dolls and The Heartbreakers):
My favorite guitarist of the punk generation, Johnny Thunders playing style combined 12 bar based progressions with a signature intensity that would make him an essential influence on bands such as The Ramones and The Sex Pistols. Perhaps one of the most attractive elements of Thunders playing are his licks reminiscent of Chock Berry from a time where most guitar solo's were long winded and technical, Thunders simplicity and sloppy style has afforded his work a certain charm which many of the decades most influential bands would incorporate into their own work.
Jack White (The White Stripes):
Jack White is by far my favorite contemporary guitar player, combining the signature low-fi rock sound that Detroit is famous for with strong influences from the Delta-Blues and predominantly American folk (although traditional folk from other regions can be heard across his discography). While it is clear that White is a more than capable guitar player his playing is more often than not extremely simple and the strength of his music lies in the song writing and opposed to playing, a sentiment that seems to have been lost by contemporary musicians a long time ago. This generation needs more Jack White's!
Honorable mentions go to Ron Ashton (The Stooges), Rowland S. Howard (The Birthday Party), Tom Verlaine (Television), Thurston Moore (Sonic Youth) and Robby Krieger (The Doors).
...I'm sorry that ended up being MUCH more self indulgent than I had planned (I just have a lot of time to spare, heh).
on this thread are all legends imo. Mac briefly mentioned the Banjo, I'm not into Bluegrass but I've heard some 'instrumentals only' played by D. Wessman Old Joe Clark/Johnston Boys etc (man they rock) off a CD given to me a while back called Southern Mountain Bluegrass Instrumentals, including 
