Over the years, I've tried many different strings, capos, tuners, picks, etc.  I've come to the conclusion that, while there are large price ranges in each of these items, there is no 'best' - just what each player 'likes' the best.

I  have found a few items.  The first is a revolutionary product that improves the sound of every guitar.  I've tried it on all types of guitars, new and old and the results are always dramatic.  It is the ToneRite and it dramatically improves what they call the 'Play-In process'.  It 'sits' on the strings of your guitar and you control the vibrations to get the tone you are looking for.  Click here to see it on one of my guitars.  ToneRite explains it the following way:

The Play-In process involves the individual components of an instrument learning to resonate as a whole instead of against one another destructively.  This process occurs due to vibrational energy that effectively transfers into the instrument to de-dampen it.  The result of this process is added volume, resonance, dynamic range, playability, etc.

I'm proud to be a dealer for ToneRite.  You can buy slightly used ToneRites here for only $119.00 with free shipping.  Click here to see how it is used.