Joni Mitchell's 1956 Martin D-28
With some of the greats, it's hard to know where to focus your attention. When young, Joni Mitchell had a three-octave vocal range, which helped make her one of the most extraordinary singers of her generation. Setting that aside, she's also an incredibly gifted lyricist who's penned unforgettable lines that have become part of the collective consciousness. Now, add on her songwriting skills, which have resulted in dozens of innovative, intricate and beautiful tunes.
Finally, top it all off with the fact that she can wield a guitar like few others (not to mention play mandolins, flutes, pianos, et al). One of the things that makes her guitar playing so distinctive is the unusual array of tunings she deploys. Apparently, when she was a child, Mitchell had polio, which weakened her left hand. Unable to play certain chord shapes, she adopted inventive tunings to compensate.
In 1966, a Marine captain returning from Vietnam, gave Mitchell a 1956 Martin D-28 that had survived a shrapnel hit. Mitchell loved the guitar more than any other and speculated that its amazing sound was due to the explosion structurally altering the wood. Sadly, in the mid-70s, somebody stole the legendary instrument from an airport luggage carousel and it was never seen again [source: O'Hara].