One of my favorite composers of all time is Fernando Sor, an 18th century guitarist who is justly famous for (among other things) a set of guitar studies that remain part of the classical guitar canon to this day.  One of the reasons for that is because the studies not only vary in difficulty (as one would expect), but also because each of them is richly expressive.  That is, even the easiest one -- a piece that could be read and played by someone with, say, a month's experience on the classical guitar -- has been performed in concert, by professional guitarists.

I'm currently working on this one:

Sor's Andantino in B Minor, Op. 22, nº3

(I'm not much of a fan of that guy's playing. Very wooden.)

That's actually not a study, but rather a real concert piece.  It's got some tricky bits to it, so I've been preparing for it by reviewing some of Sor's studies, most notably "Study #5," an arpeggiated jewel in B minor.  Here'sa dude playing it (and very well, I might add):

The great thing about this piece is that it is incredibly simple, musically, but allows an enormous range of interpretation and expression. I found years ago that with the temp doubled, it really takes on an entirely different (but interesting) character.

Eventually, I want to get back to playing Bach, especially BWV 997 (or, at least, the prelude and Fugue). That one could occupy me for days at a time, several years ago. Here's another random youtube dude playing the 997 prelude:

He made a few mistakes, but otherwise played fluidly and well -- and lemme tell you, this piece is pretty seriously difficult.  Here's what appears to be a music recital with a fellow playing the fugue that follows the prelude, again very well:

I like one of the comments on that last one: "This is my favorite piece to play by Bach. If you haven't played it you can't fully appreciate it's richenss and density. I find most listeners eye's glaze over and are lost after the first 10 or so measures, which I don't mind cuz then I feel alone with the piece and enjoy it all the more. Again, great job, this one takes a lot of courage and force of will."  I could have written that comment myself!  (Although I haven't been able to play this for several years, since I laid down the guitar.)

Honestly, I love the fugue.  I think that maybe I should travel back to Bach's time.

Oh, did I mention that I'm about to buy a new guitar?  Yup.  It was either a trip to Nepal or a new guitar, and really, sleeping in tents is way over-rated.