Okay the last four won too many votes. To compare the popularity of the others, I made a new poll excluding them! And I randomly included 14 because I like it! Plus numbers 26,27 and 28.
In the case you remember some of these by nickname/key and not number:
25 - G minor
31 - 'Paris'
My favorite pieces by Bach are his Violin Partitas and Sonatas; I love them so much that I have been tired of them for awhile now, and so I am very happy to have discovered Telemann's wonderful music for solo violin.
Excluding piano, I can't even name that many pieces for solo instruments...