In addition to Sal Savador, I have also made custom instruments for many other professional guitarists, some of which are listed below:

six string jazz guitar - Mundell Lowe

7-string jazz guitar & 7-string classical - Bucky Pizzarelli

6-string jazz guitar - Joshua Breakstone

6-string jazz guitar & classical guitar - Joe Carter

7-string jazz guitar - Howie Collins

two 6-string jazz guitars, 7-string - Tony Lombardozzi
           jazz guitars & solid-body electric                                  

7-string jazz guitar - Howard Morgen