Instruments that should be more common

Violas should get more play.

Usually only heard as part of a string quartet, or blended to hell in a symphony, they actually sound very nice on their own. As capable of intricate melodies as a violin, albeit with a 5th lower range, the increased size gives a richness of tone suggestive of what happens when the pattern is grown to a cello.

The Musical Anoscope.

Celestas and harpsichords. And carillons.