For those who are still doubters of this wonderful instrument, here are a few links regarding the melodica in jazz and music today. In the first video, pianist Jon Batiste talks about his love of the instrument, and the tonal possibilities that it has. The second video is an extraordinary rendition of Astor Piazzolla's Libertango by Masa Matsuda. It has to be see to be believed.
As far as tone is concerned this is my favourite. Mario Duenas has a quite beautiful and expressive sound. There are other several good videos to be seen on his Channel.
To wrap it all up have a look at this article from the Jazztruth blog. A humorous and insightful discovery of the melodica in jazz today.